Use them by double-clicking on them or right-click on them and select use and it will open a window where you can trade them for the current research materials.
A question that I have yet to see an answer for is what is suppose to happen to all these defunct schematics. With the exception of the Horta, the schematics are now inventory junk with no apparent use in game.
Comments
Actually, you use the Horta Schematic too now. It works a lot like one of the Holonovel code fragment or temporal beacon missions.
My character Tsin'xing