Montjuic cable car and Castle. So confused!

I Googled it and saw on the Google map that bus 150 "Castell" is directly in front of the castle and can be picked up by Plaza Espanya. This really seems like the easiest option:
https://www.tmb.cat/en/barcelona/buses/-/lineabus/150

Or just ask the taxi cab or write down "Telefèric de Montjuïc" if you're determined to take the cable car. It doesn't seem that confusing.

Personally, the best way to get to the Montjuic cable cars is taking the Metro to Parallel metro station then riding the funicular that drops you off at the first cable car station. However, if you want to go by taxi, just write down the address or ask to go to Parc de Montjuic, Av. Miramar opposite the Montjuïc Municipal Swimming Pool.

The cable car ride doesn't take that long-maybe 15-20 minutes. We didn't tour the castle but walked through the park on our way back down. I will mention the Joan Miro Museum, as it's a fascinating museum with a great roof view.

So I would tell the taxi driver to take me to the Parallel metro station? And what exactly is the “funicular”? Is that another station that requires a ticket purchase?
Sorry to be so dense.
Here is what I was hoping someone could tell me:
Get a Taxi.
Tell him to take you to (name here)
When you get to (name here) buy a ticket( if needed) to (name Here) ?

Then where does the cable car ride and Castle fit in to all this and how/where?
I just don't understand all the different things one needs to do to just get to the Castle and cable car.

Okay I found this:
How to get to Montjuic
1. Funicular
This funicular railway connects Montjuic with the Metro Transportation system at Paral·lel Station, Lines 2 and 3. It’s the fastest an easiest way to get to Montjuic when you’re in the Metro. The trip is already included on your regular Metro ticket.
(But I don't have a Metro Ticket just the cable car ticket so would I have to purchase a "Metro" ticket at the Paral-lel Station?

And then it says this:

2. Cable Car (the fun one!)
Right next to the funicular Station, lies the Montjuic’s Cable Car. This ride takes you directly to the castle of Montjuic with photogenic views of Barcelona. Option number two, is taking regular bus #150 which also stops at the castle. Buy your ticket to Montjuic’s cable car here.
Built in 1931, this cable car system is located in Barceloneta. The journey lasts around ten minutes and it’s the fastest way to get to the mountain from Barceloneta Beach. The view of the seaport and Barceloneta from 70 meters high is priceless.

So is there more than one way to take the cable car ride? Is says from Barceloneta Beach?

Call me CONFUSED!

• There are two cable cars -- to visually see this.... https://ibb.co/bP5auF -- one from La Barceloneta beach to Miramar in Montjuïc, called Aeri del Port (in red), and another at 1000 yards (15' walk) from there, called Telefèric de Montjuïc (in blue), which takes you to the fortress on top of Montjuïc.
• There are several funiculars in Barcelona, the one you mention, funicular de Montjuïc, takes you from Avinguda Paral·lel (pronounced like 'parallel' in English) to the Teleferic de Montjuïc above mentioned. For this transport, you can use, if you have it, the T-10 travel card or the HolaBCN travel card.

For info: A "funicular" is a type of cable railway in which a cable attached to a pair of tram-like vehicles on rails moves them up and down a steep slope, the ascending and descending vehicles counterbalancing each other.

@Enric Thank you I understand at least that part of it now. I have no other tickets or cards of any kind other than the Cable car ride tickets that are not from Barcelonette Beach. It the other one I have.
Am trying to figure out how to take a Taxi to the nearest point I need and then what to do from there as far as place any any other thicket purchases I will need to make.
Thank you for your reply.

Okay, I think after finding different snippets everywhere on how to get there I have assumed the following:
I can get a Taxi from anywhere I am in Barcelona and tell him to take us to the Paral-lel Metro Station. On the instructions I have found, it says once one arrives at the Paral-lel Metro Station, just follow the signs to the "Funicular de Montjuic" and that I can just use the same Metro tickets on the Funicular Train. But I won't have a Metro ticket at this point so my questions are:
1.So far, do I have the above mentioned correct? and
2. Can I purchase a Funicular de Montjuic ticket at the Paral-lel station since I won't have a Metro ticket at this point?
THANK YOU!

1. YES
2. YES

THANK YOU EVER SOOOO MUCH!

If you are spending a full day, I prefer to start at Placa Espanya. Take the escalators up to Montjuic, visiting MNAC, the Olympic Ring, and along to the Miro Museum. The teleferic will get you up to the Castell, and the funicular will get you down to Parallel.