You will be endorsed by the immigration officers upon your arrival before you are issued with a permit. Make sure you go personally. You may have to carry your passport (also some passport photographs) or voter's registration card. If you plan to travel by road, the endorsement is done at the entry points in Phuentsholing, Samdrup Jongkhar, and Gelephu. If by flight, you will enter from the Paro Airport.