Both the Delta Glider IV and the Shuttle Fleet (through the use of AutoFCS add-on) have automatic re-entry auto pilots. First you should align plane with the landing site (or wait until your next orbit crosses the landing site.) Read the docs on how to do that. Most spacecraft need to retro burn near Australia for landing in the US. There is an ExtendedMAP MFD which allows you to see your path across the Earth many orbits in advance.
On DG when returning to an Earth Base, turn retrograde using the default AP and burn main engines until you see the trajectory line on the MAP MFD turn orange or end over the landing site. Turn prograde and activate the DG Reentry AP.
On the Shuttle Fleet, the AP will do everything and land automatically when AutoFCS is activated through the External MFD feature of Orbiter. You need to activate AFCS leaving India/Asia. The burn will occur by the time you each the Indian Ocean just West of Australia. Learn how to control the ship manually by watching what the reentry APs do. You will understand better if you activate the GPSMFD (Shuttle Fleet) and observe the displays.
Orbiter crashes when loading scenarios is usually caused by the add-on not being fully or properly installed and/or add-ons on which the desired add-on depends are not fully installed. The Shuttle Fleet has installation documents in the root of Orbiter with links to required add-ons. Be aware sometimes these links go away or get substituted with later versions. OrbiterDiagnostic stand alone program can also list typical problems with Orbiter and scenarios, but does not necessarily instruct you on how to correct the problem. Some scenarios may never work and should just be deleted or ignored. Add-ons and Orbiter versions can cause Orbiter to behave much differently than when the add-on was initially created and tested.
-Pv-