Ok so like on the 172 g1000 for simulator, you hit the AP button to turn autopilot on. it will capture what your currently doing (maintain your bank, heading and altitude). So if you're in a climbing turn to the left, it will hold that for you. If you're flying straight and level, it will hold that for you. If you have just taken off and are climbing out, it will continue that for you. There's also a red button on the yoke that disengages the AP.
if you have a flight plan in the system (you'd hit the FPL button and input waypoints or airports), you can hit NAV (or GPS) and it will follow the flight plan, using the magenta line in the middle of the heading indicator. sometimes this magenta line will be to the right or left of center so the autopilot will turn the correct direction to bring that magenta line back to center, this brings you back on course (you were off course).
if you're doing instrument approaches, you'd hit APR which would capture the vertal and lateral guidance of an instrument approach and follow it down to minimum altitude for that approach. you'd have to load and activate the approach first. i wont go into detail with that cause you wanted easy to understand and i dont want to teach you instrument flying.
ALT button will hold or capture an ALT that you have bugged on the PFD (primary flight display). on the 172 PFD, altitude is the little box above the altimeter where it might say like 1600 or a set altitude. you can change this with the altitude knob
VS is vertical speed, telling the plane how fast you want to climb or descend. this can be combined with the ALT button, so you'd set an ALT to capture, then set the VS tell it how fast to climb or descend, and once it reaches the ALT it should turn off VS and hold that ALT.
VNV is vertical navigation, has to do with instrument approaches i believe, i havent used it too much. the autopilot we have in our 172 doesnt have this button.
BC is to track a back course for a localizer, again instrument flying.
FD is flight director that displays a guide on the artificial horizon, which shows the attitude of the airplane, but does nothing to control the plane. The guide represents a reference of an airplane attitude that will follow the parameters set for the autopilot. The pilot can manually fly the plane directly where the flight director indicates, and by doing so the plane will follow the parameters set for the autopilot.
Also some autopilots have capability to climb or descend at a certain airspeed, this is the FLC button.
As u can tell depending on the plane the autopilot can be more sophisticated or not. This is a picture of a less sophisticated one that I use sometimes, doesn't have a FD, FLC, VNV button etc.
if you want to look up waypoints to put into your flight plan or airports, you could use skyvector.com use the World VFR map or the Enroute L-21 (instrument map) which will have better depiction of waypoints you can use along your flight plan to a determined airport. Yes you could just go direct from airport to airport, but pilots use highways with waypoints in them between destination airports.
But for simplicity you could say you're in miami so KMIA is your first FPL airport then say you want to go to tallahassee you'd put in KTLH and then if you were in the air, hit autopilot and then NAV (or GPS) it will fly you straight from miami to Tallahassee.