Quick Questions About Check-in Etc.

We purchased our spirit air tickets from cheapoair (without reading reviews). After reading up, a little afraid. We are not planning on checking anything nor carrying anything other than bookbags which should fit under the seat. We will print our boarding passed at home. Can we just head phir ugh security or do we need to go to the check in counter? Do we need to prepare ourselves for any other fees? We are flying from Baltimore airport to fort lauderdale.