National Rail travel card on the tube

It IS confusing.

What you are buying is a one-week travelcard (probably zones 1 & 2) that covers all your transport on tube, buses, DLR and a few other bits of transport within central London.

However, due to a kind of loophole, if you buy this travelcard at a National Rail station ticket office (like Victoria, Paddington, Waterloo, Kings Cross) then it also gives you 2-for-1 at major attractions.

Remember that both travellers* need to have the travelcards in order to benefit from the 2-for-1 offers, and you will also need passport-sized photos ready when you buy the cards.

*You mention "I" which suggests you're travelling alone. If you are, there's literally no point in seeking out the 2-for-1 offers as what's the point in buying two tickets when there's one of you?

Thanks sorry. Yes there is two of us. I think I read I can't use the pass in the machine at the tube station. That we need to use a manned gate ? My thought is if we use the hop on hop off bus (my mom likes them) and just buy a one day travel card from national rail. The problem is we have already purchased our London eye tickets using the 2 4 1 offer. It states they will ask for a travel card. If we get to the eye with out the travel card could be just pay for the second admission if asked. We have reservations
Thanks

Where have you read they can't be used at the automatic gate? Each gate has a yellow pad for Oyster cards and a slot for inserting paper tickets (mag stripe face down). Fairly similar gates are used on National Rail and TfL stations in London and millions of people commuting into London use them every day (or a longer season)

As National Rail says

Travelcards can be issued in a range of zonal combinations and subject to the zones purchased, you can use your Travelcard on:
London Underground (the Tube), DLR and National Rail services (but not Heathrow Express or Heathrow Connect services between Hayes & Harlington and Heathrow)
All London Bus services (except some special services and excursions) regardless of the zones for which the ticket is issued
London Trams services, where the Travelcard is valid for travel in Zone 3, 4, 5 or 6 or any combination of these zones.

However, do not buy a one day travelcard of any kind within London as they are now ridiculously overpriced.

Also ignore specific HoHo buses in London for general transport as they are inferior to regular services, which with a Travelcard you can HoHo on anyway.

The manned gate advice only applies if you are traveling on a train from another city to London. If you put your ticket into the gate at your final destination, it is not returned to you and then you no longer have the train ticket showing travel to London that allows you to use the 2 for 1 offers. Using the manned gate, you would show your train ticket - not Travelcard - to the attendant and let them know you need to keep the ticket.

Thank you so much I am usually a good traveler but I making changes to my trip on the fly as I am finding that my mom is not able to do as much as I hoped. We are in Paris and the moment and she is finding the stairs to the metro hard. We did the hop on bus and she enjoyed it. I will grab the travel cards at Earls Court. I assume that as long as I have separate pictures of us both I can buy two cards and leave her with our luggage. We are arriving by train from Paris.

Use ordinary London buses - still the red double deckers, but much better for getting around than the Hop-On Hop-Off because (a) cheaper and (b) you don't keep having to travel around in a big loop to get anywhere!

As you have already stated yourself, you will need to buy at a National Rail station, not Earls Court for the 2For1 offer - since you are arriving by train, do it at Kings Cross St Pancras mainline station (step free access to the underground at this station).

Incidentally Earls Court also has step free access from street to platform, but that won't help at the other end of your journey every time.