I forgot to include my wife's ira contribution that she just made How do I amend check and see if I want to amend my return and what does it cost to amend my return?

My wife was making a 2019 for 2018 that I forgot to include on my return.  How do I amend the return and what is the cost of making this change?     

She contributed $6500 to her traditional IRA and I forgot that she was going to do that.