1. buy a counterfeit pass
2. get a massage
3. Follow the story
4. pay 500 to make one on tattoo parlor, or you can make it yourself by combining ink pen with any counterfeit passes (after you learned how to do it, ofc)
5. bring it to the UNA gate
6. profit
EDIT
0. you need to know where to buy it first (ask the clubs receptionist and the dude on the slums rest area)