Can I sign up for my stimulus check through turbo tax or is it only through the IRS?

One does not "sign up" for a stimulus check unless you know for an absolute fact that you will *NOT* be filing a 2020 tax return. If you do sign up and then later find you need to file a 2020 tax return, you will not, under any circumstances, be able to e-file that return. (unless the IRS changes the rules on that between now and 2020 tax filing season).

Only the IRS controls when or if a stimulus payment is distributed.

Go to this IRS website for stimulus payment information FAQ's - https://www.irs.gov/coronavirus/economic-impact-payment-information-center

Use this IRS website for stimulus payment status - https://www.irs.gov/coronavirus/get-my-payment

Use this IRS website for get my payment FAQ's - https://www.irs.gov/coronavirus/get-my-payment-frequently-asked-questions

IRS website for non-filer stimulus payments - https://www.irs.gov/coronavirus/non-filers-enter-payment-info-here