Are you sure you're in the correct forum? Ms Flightsim is discussed elsewhere.
You can create temp waypoints in the nav database. Just input a name not currently used on the nav ref page and then specify either coordinates or bearing/range from a stored waypoint.
All waypoints have coordinates in fine text published on the Jeppesen plates.
The easiest way is to insert waypoints directly in the legs pages using range/bearing from stored waypoints to build your routes.
Check chapter 11 in FCOM2 for more info.