An affiliate manager is usually hired to tap into local affiliate resources. Affiliate managers are usually influential in the niche & in the country/continent. Affiliate managers can recruit more affiliates for you. Some managers work on a commission basis while some on a fixed monthly amount.
Now coming to how you can promote your program.
1) You need to be active & promote (paid) your programs in forums for your niche where affiliates are active.
2) Do press releases, blogs, articles etc to create awareness regarding the program, its benefits, product, etc.
3) You can run some promotional campaign for a week or 2, PPC to create a buzz about the program for affiliates to join you.
However, do ensure that you have your payout options, promotional material & other stuff affiliates need ready by the time they join you or it will cause a negative impact regarding the program.