Hi! Often, new tracks come in .zip files,
There you'll have the .dat file (that's the track, and goes into the CIRCUITS folder, with this name: F1CTNN.dat - where NN is the number of the track, from 01 to 16)
And the texture files: .jam files.
Generally, the tracks come wth instructions on how to install those texture. Usually you'll have to create a new folder in the GAMEJAMS folder (Instructions with the name of the folder usually are inncluded) and put the .jam files into that folder.
Sometime, the files have the .jad extension, and the zip file has a CONVERT.EXE that you must execute with DOSBox to convert them into .jam
Finally, you'll want the Fragata Gp2 Track Manager to manage tracks