Once you obtain an augment's schematic through a slicing crew mission, you will have to craft the augment. You can then equip it in an item's augment slot. Different grades of Augments require different grades of augment slots to work, although a lower grade Augment will work in a higher grade augment slot.
An Augment can change the required level for an item.
There are various types of Augments, each one augmenting a different set of stats.