How to connect LED tape strips in separate locations to one power source?
You can use either one power supply or many. The important thing is that you use a power supply that is listed for enclosing in a wall or attic. Something like in this picture: 

Any light strip you buy that is designed for permanent installation should come with such a supply and will be listed by UL or similar.

I don't recall seeing LED tape strips that come with a proper wall box, rather I have seen them come with plug in power supplies or transformers that most municipalities will not allow to be buried in a wall. It doesn't mean they don't exist, of course. Regardless, check with your code office to see what supply is permitted in your area. Perhaps they will allow a simple transformer to be concealed. That would surprise me, though.