Can not upgrade

[Tin Soldier]

I am certain I am missing something simple, but I can not seem to figure out how to upgrade. I have money, new units are available for purchase, but I can't figure out how to upgrade what I have.

TIA

tanner

[Seuloup]

At the beginning of a mission when you are in you're Army Management screen, click on any unit with a big gold arrow (vs the triple arrow for perks) and then on the right click on the up arrow below the Perks arrow. If that doesn't help, let me know.