The SBB trip planner has all the public transit in all of Switzerland, so it knows of all stops, and also knows all street addresses and a lot of POIs.
Normally when you start typing in a place name you will see a list, and the most important stop will be at the top. So when you type in Luzern you will get “Luzern” at the top, and that is the station, as stations are usually just named after their town in Switzerland.
If you know which bus stop you want to go to you can select that. If you do not know what to select just enter the street addresses of your accomodation, and the system will find the best stop for you.
Regarding your first trip: You can look up bus stops on google maps, or in the trip details on sbb-tickets.cc, where you can call up a map as well. The bus will make several stops en route, you just get off where it is convenient for you. The way tickets work it is not necessary to have the exact right stop on the ticket, having the correct town name is sufficient.