At the right hand side of your screen you have a list of augmentations, but I can't find any guidance on how to enable them.
Probably very simple, but this has stumped me and my son for a while.
When I played on the Xbox 360, they were mapped to the D-Pad. This appears to be the way they are mapped on the PS3 as well. The orientation of the augments on the display indicated which one was activated by which direction on the pad.
On PC, it's the function keys (F1-F4). You might want to check out this keyboard layout page. It lists the controller layout on consoles, and I assume the default keys on the PC.