First of all, it's strongly advised to sell only reserve drivers. So you must own more than 2 drivers (I'm assuming that you are in a 2-car League)
You question is related to sell drivers directly to someone else (I saw a complete question in your League wall)
Next step: you'll have to copy your drivers link
After that you send your driver's link by message and sell your driver instantly, by doing that you assure that your friend have to pay 3 tokens and guarantee a private sell.