Just to be clear, you want to start a fresh game with a totally new career?
If so, you should see the screen above and can select 'Start new game'
Another way to start fresh on the PC is to delete the profile manually, but you have to disable the Steam Cloud first, or Steam will try and replace the files you delete with the backup files in the cloud.
1/ Run steam > Right Click on F1 2012 > Select 'Properties' > Select the 'Updates' tab > Deselect (Untick) the 'Enable Steam Cloud synchronisation for F1 2012'
Now the cloud is disabled.
2/ Browse to YourSteamInstallDrive:\Program Files (x86)\Steam\userdata\xxxxxxx\208500\remote folder
xxxxxxx = Your Steam ID number, everyone has a different number here.
208500 = F1 2012 profile save folder. 208500 is Steam's Application ID number for F1 2012
In the 'remote' folder is your actually game save folder, there are 15 files in there that look like this - savegame@profile0#aggric czvkekg wom miwc. Make a backup copy of all of the files if you wish, but delete all the files in the 'remote' folder
Start the game and you will have to create a new profile