Find out your college's allowances for deferral of an undergraduate degree. Some colleges will allow deferral for employment or traveling, but not for taking courses elsewhere. Your college's admissions' office should detail allowances on its website. Alternatively, you can call the office directly.
Complete an admission deferral form on the website of the admissions' office of the college that accepted you, if you determine you are eligible. Send the form into the admissions' office or whatever address the website indicates. Some institutions may only require you to email your request directly. Include your personal information, such as your full name and student identification number.
Wait for an approval from the admissions' office either by mail or email with instructions regarding how to enrol in courses next year or semester.