If you are in F-2 status, you may study part-time at Calvin. This means you may take no more than 11 credits per semester. If you wish to study full time, you must either depart the U.S. and apply for an F-1 visa before returning, or apply for change of status while remaining in the U.S.
If you apply for change of status, it is strongly recommended that you work with an immigration attorney on your application. It can take a very long time for change of status to be approved, and you may not study full time until you are approved.
Generally it is fastest to seek F-1 status by departing the U.S., applying for an F-1 visa, and then returning.