Upgrade nanosuit crysis 3

When I should update my nanosuit in Crysis 3 I don't know how to do it.

I press "H" and get the menu. But how do I choose the upgrade I want?

I can mark the upgrade but which key should I press then?

Scroll the upgrade you want to the corresponding yellow box. If there is a red thing with a number 1, 2, or 3 on the upgrade, the Unlock button should be present and usable. If you press the Unlock button, whatever locked upgrade in the yellow boxes will become unlocked. You can store 3 sets of upgrade packages at the right of the screen.

If the upgrade is already unlocked, there won't be an Unlock button. Simply leave the desired upgrade in the yellow box.