1. Add the sponsor to the list in the Sponsors area of admin. (Fill in their company name, website, upload their logo, etc.)
2. Add a “sponsorship” to the sponsor profile for the season and level they signed up for.
That will allow the sponsor to appear on the public website for the selected season.
The "Sponsors" list in admin is meant to be a resueable library. So, if this sponsor supports you in future years, you won’t need to re-create the sponsor. You’ll only need to add a new sponsorship for the new season and the level they signed up for that season.