How would I go about switching my bi-weekly payroll to a weekly payroll?

Unless you are a large employer and are required to remit withheld taxes after each payroll, your payroll period frequency isn't tied to your payment period frequency.

However, if you have requirements to make (for example) a health insurance deduction for each month a specific amount, and you had that set up before, you will likely need to adjust the amount withheld on each check by editing the employee records and updating the deduction - and other similar ones.