To use the new track, you need the NOCDROM utility. You can download this utility at  http://home3.swipnet.se/~w-36707/Romeos/Cool.html. Once you have installed NOCDROM, there is a folder created in your GP2 folder called "circuits". In this folder there are 16 files called F1CT??.dat (where ?? is a number from 01-16). These are the track data files for the 16 circuits in GP2, where F1CT01 is Brazil (slot A), F1CT02 is Pacific (slot B) and so on, up to F1CT16, which is Adelaide (slot P). 

Now this is what you'll have to do: 
- Make a copy of all original tracks, so you don't lose them. 
- Download tracks that you need at these page. 
- Replace original tracks by tracks you downloaded. 
   (Copy f1ct01.dat that you have downloaded instead original f1ct01.dat, 
    f1ct02.dat replace by f1ct02.dat ect. in your GP2\Circuits\  folder)  
- Drive and have fun. :-)
- Required tracks with full graphics you can download at Pieter/Sion's GP Homepage.
- But remember that you need rename tracks data files due to this schedule.

Good luck!