according to the rules, you make a first aid + logic (2) skill test. Each hit above the treshold (2 in your case) heals 1 box. So Clem heals 2 boxes. You can also only heal a maximum of your skill rank (I don't know how much that is). It can only done once and not after magical healing. If I recall correctly you can apply magical healing after first aid, so if more has to be healed, I can do a magical healing.
for the roll: Clem is street sam right? I have a -1 per 2 points of lost essence, so I need to know that to know my penalty.