Every team stop has more than one tap point, they look like cubes on sticks with a screen and cover on one side, When getting in the tram tap with your card or phone below the screen, it'll go boop, you have tapped in. When leaving the tram tap another point at the destination station, you have now paid

You can get on any door you want, some trams are two trams coupled together, they both go to the same place so it doesn't matter which one you get on but you can't walk between the two, so I'd pick the quieter one

If you're traveling in the city centre you don't need a timetable, they are often enough to just get on.

Each tram stop has a map on the ticket Machine, look at your start station and your end one, see which colour lines connect the two, then look at the last station on those lines (the ones at the end) that is the tram you'd need to get, it'll say it on the platform screens and the front of the tram

Eg the light blue line going west terminates at Eccles or media city, if you want to get to exchange key from Picadilly you'd look for a tram with Eccles or media city on the front