Whatever you are thinking about flying inside, about it being safer and unable to fly away, forget that. Take it out in a large open area outside, and only take off after you see the "rth updated please check it on the map". Then check it on the map to be sure it has saved. Also remember to check/set your RTH altitude higher than the highest obstacle in your flight area.
I may go overboard, but my routine when flying is this: (on the app)
Check RTH point on map
Check RTH altitude
Check/adjust max height and altitude (as a new pilot this and beginner mode are your best friend) Out of the box I think these are set at 20 and 30m respectively. Helps alleviate fears of flying away your first few times out.
Check sensors (IMU and compass)
Check wifi channel interference
Also if your homepoint takes a while to update, just do all the rest of the preflight check first, and by the time you get through those few tasks the homepoint should be updated and shown on the map in yellow.
Also learn the attitude indicator within the go app, it helps show the direction of the aircraft as well as what sort of wind the spark is seeing up where it's flying.