How can I convert money from Traditional IRA to Roth IRA each year, and how does that impact my taxes?

How much can I convert from Traditional IRA to Roth IRA each year, and how does that impact my taxes?

I'm 68 and haven't begun pulling money from 401K or IRA's yet. I don't plan to pull from the Roth IRA since there's RMD. However, when I have to start taking RMD from my Traditional IRA, it will force me into a much higher tax bracket. How can I convert money from Trad to Roth IRA? How often, and how does it impact my taxes?
Thanks.