I filed with turbo but want to switch to another site, it says I cannot amend until 2/15 but it says my refund should be here 2/12?

If you already filed, you will not want to amend until your original return has been fully processed to avoid unnecessary delays. This is one reason why amending is not available until 2/15. I'm not sure what you mean about wanting to switch to another site.

How to amend my return?

If you already e-filed, you cannot file another tax return somewhere else.  The IRS will not accept two tax returns from you.   If you e-filed you have to wait to see if the IRS accepts your return.   If they reject it, then you can abandon TurboTax and go anywhere you want.  But if the IRS accepts your e-file, that's it.  You wait for the IRS to process the return.   If you made mistakes you amend it after it has been fully processed.