How do you get from Tate Britian to Chelsea Old church in London UK?
I don't know anything about your or your requirements.
A very general answer is to either walk along the river for around 40 or 45 minutes or take a bus to Victoria and change to a different bus to complete your journey in 45 to 50 minutes, or more if the traffic is bad.
Often the first bus will be a C10 and the second a 170, but there are others.
Best thing is for you to go to the official journey planner of TfL who are in charge of public transport in London. Their main entry website is at https://tfl.gov.uk/
You can adjust your preferences by type of transport, your accessability needs, amount of walking and many other options. Make sure if you are experimenting with the site to put in the London time you want because if you don't it will put in the local time which may be in the middle of the night if you are halfway around the world when you look it up.
You can put in an address but it works just as well if you put in landmarks or public buildings. It understands Tate Britain to Chelsea Old Church.