Accepted, Do I Need To Enroll?

[MDW2447]

I applied and was accepted to TESU last month and have a question: 

It's my understanding that being accepted will "lock in" the current catalog, but after reading some other threads I'm wondering if I need to enroll in a class in order to do this? If true, seeing as how it's 12/12 now, I may have missed the boat on this?

I plan on following the BA Psych plan listed on the Wiki. I'm a SAHM with kids in school, so I'm going to attempt to complete in one calendar year.
(Currently working to finish behavioral statistics on ALEKS before it expires with ACE at the end of the year.)

Thanks for any clarity around this.