If you’re crossing over from Egypt, when the ferry docks you will disembark at the Customs and Immigration terminal. It is a few kilometers outside of the town itself.
Wadi Halfa itself is a small town on a hill with one main street and a lot of traffic once a week when the ferry comes in. The processing for entering Sudan is usually painless but plodding. Though it has many steps and you will probably have to ask directions a few times along the way. Don’t worry about asking for help, the people are friendly even if they are wearing a uniform.
Even if you don’t hire him it is likely that you will meet Medhat or his brother in Wadi Halfa as they often start adventures from the little town.