How does using F1-F4 on allies work? Is there something similar for use on enemies?

Solution 1:

Ok, to help assist you I will use Shen as a primary example, since he is my main tank and I feel most comfortably using him. So his ultimate is called Stand United, this allows him to teleport to an ally and add a shield to them to help prevent them from being killed. So on the left hand side of the screen you have images of your teammates champs. You can click F2/F3/F4/F5 to select the team mates on the left in the order that is listed on the left side of the screen image or you can click on the image and it casts your spell on that champ. If an ally champ is in the cast range for a shield you can click on them and it will cast or f2-f5 depending on your option. The F keys only relate to your team mates. As for enemy hotkeys to date there are no hotkeys.