How do I change my rental income to VERP? (Vermont Emergency Rental Program) assistance. I got an IRS notice that said I claimed renters rebate and I didn’t.

I'm not sure you need to amend your return.  Vermont Emergency Rental Assistance payments are normally sent to the landlord or in very rare cases to the tenant who then submits to the landlord.  The landlord will get a form 1099-Misc showing those rental payments.  The landlord then enters the income in the "Rental Property" topic on their tax returns.  It is income to the landlord and reported as such.  There is no identification on the income entry for VERP or Renters Rebate.  

So there would not be a need to amend unless you as the landlord did not list the income item for the rental property.  If that is the case, after reopening your return using the "Amend" option, you will need to revisit the "Rental...income" topic in the "Wages and Income" section. Edit the rental property and "Add Income."  Select the 1099-Misc category.  

NOTE:  Be sure you have copy of the originally filed return before you start the changes as you will need information from that to complete the amendment.  

The tenant does not get an income form (1099) and does not enter the payments on a tax return. 

You should verify the source of the letter (IRS or Vermont) and determine what the letter is asking you to do.  It is not typically to amend a tax return.