I am getting some new tubes for my amp, and I want to do a 24-hour burn in. How?

I typically go through an upgrade cycle, upgrading most components. Breakin quickly becomes a problem... tubes need a dozen or so hours to get rid of that crisp sound, but good new components require 400-600 hours to sound right. If you buy a new component and want to audition another one... you need the first broken in. If you upgrade five or six components, then interconnects... it is a mess. Most of my equipment sounds good... but not magical until after 150 - 200 hours. I have invested for magic, not just good. I’ve learned about break in for decades... I want to get through it as fast as possible. Life is too short. My last upgrade cycle took over six months, That was fast... because of break in. For various reasons I had to break in three new identical tube amps... I can write a thesis on the sound changes of a breaking in Audio Research Reference 160s. Audio Research puts time on the tubes prior to sale, so there is no obvious “new tube” break in... it is all component break in.

You hit the switch that says "Power", pick out some music and enjoy.

"...1. Connect amp to speakers...2. Plug amp in...3. Turn amp on...There is more? Really???!

Check bias if required. 

@hilde45 

I just did some reading on other forums that it gets rid of the harshness of brand new tubes.

Even so, no big deal, generally harshness would vanish somehow quickly and bass will get tighter. You can have the pleasure of knowing how a particular tube will sound in its lifetime.