For the first week, you must wear the tightest briefs you can fit in to. Preferably colourful ones. If you don't have any briefs, buy some. If you have briefs but they are your regular size or even 1-2 sizes smaller, buy some new ones.
If you were a size Large regularly, I'd expect at least a size Small, for example.
Also bonus points if you wear largeish trousers/shorts with them, so some of the briefs are showing over your waistband.
Pics would be great, even if it's just of the briefs you intend to wear.