How do I use Unity in Mass Effect for Playstation 3?

You select the power in the Power Wheel to activate it. In the first Mass Effect, Unity does not consume medi-gel upon usage.

Medi-gel will not revive a fallen character unless Shepard has First Aid Specialization, which can only be obtained if Shepard is an Engineer or Sentinel and chooses the Medic specialization class later in the game.

in the first mass effect, there should be a power circle, and in your slot, there should be a symbol or icon that shows the word unity, and shows a orange picture of 3 people halfway up standing together. You can use it if all of your squadmates get knocked unconcious and when you need backup, use it and they will get up and fight again. If you use the regular medi gel, then you wont get your squadmates up again. Be aware, you use up one medi gel if you use unity. have fun.

If a teammate goes down then you use a med kit and it will revive them

I like how all of you point of phenomenal details, and yet none of you have seemingly had the mental capacity of brain cells, to actually answer his question...XD you guys are worthy of an award for your stupidity gentlemen.