Getting into orbit is good, but in the real world you need to then return to Earth. After achieving your specified orbit you must de-orbit (by firing opposite your direction of flight to lose energy) and then controlling your rate-of-descent down to a landing.
You will find the “ATT HOLD” function useful here once entering the atmosphere to keep the rocket main booster pointing downwards.
Remember that you can land and refuel at any time during a mission, so if you have burnt too much fuel without yet achieving your target goal simply land, refuel, and relaunch.
(If you manage to land on the LaunchPad then you’ll get a points bonus at the end of the mission, and a fuel bonus if you haven’t completed the mission yet).