Saving items is very simple. There are two ways:
If you're in the categories, (let's say "T-Shirts"), you'll have the option to click on "View" right next to every item. Tap there, and you'll be directed to the product view. Subsequently, you'll have the possibility to save this item either to your wardrobe or your wishlist by tapping on the "Download" icon in the upper right corner.
If you've already loaded your item into the combyner (that's where you can create your outfits by swiping left and right), long press the item and slide your finger to the little "i" icon on the right side. After this, you'll find yourself in the product view as well and can proceed as depicted above.