How do I use the annualized income method to show when my income occurs. I need to to avoid a penalty for a Roth conversion late in the year.

When you prepare your return, go the tab for special situations and choose the penalty form, then select "annualized income method."  

It is form 2210.   Here is the form and instructions.

IRS form 2210

https://www.irs.gov/pub/irs-pdf/f2210.pdf

2210 Instructions

https://www.irs.gov/pub/irs-pdf/i2210.pdf

If you have a penalty on 1040 line 38,  you might be able to eliminate it or at least reduce it.  You can go to Federal Taxes tab or Personal tab, under Other Tax Situations and select Start by the Underpayment Penalties. You will answer a series of questions that may reduce or eliminate the penalty. Or you can elect to have the IRS figure the penalty for you.  It's form 2210.

It's under

Federal or Personal (for Home & Business Desktop)

Other Tax Situations

Additional Tax Payments

Underpayment Penalties - Click the Start or update button

And.....Make sure you have fully filled in your entire tax return, all income, deductions, credits, (1099-Rs and Roth conversions), and make sure it is otherwise complete before going thru the Annualized income Q&A section.