When you enter an unexplored system, you will only get what is in auto resolution range - around 10 ls for most smaller planets, somewhat more for stars.
If you hit the Discovery scanner, you will get the knowledge about how many bodies are in that system, prime the FSS and also resolve any other stars in that system.
Now you need to throttle down and fire up the FSS. I wouldn't know about default bindings, I always had to bind it myself. Might be that there are default bindings now. With the FSS, you can then scan the system and discover the position and composition of any planets, signal sources, stellar phenomena in the system. You can also use the good old eyeball Mk.I and parallax method to find planets and just fly close enough to them (see above) for the auto resolve to work it out. Usually a bit more tedious, though.
Then you can fly to whatever is of interest to you and fire up the DSS to map the planet, or drop into a stellar phenomenon and check out what is there with your composition scanner.