Go to the multiplayer options from the main menu and set up a ranked conquest game and during play when you see your team mate in MIA just go over to him and press
to heal your team mate. This has to be done 10 times in one match so it probably best if you put the time limit to the maximum so you get all the time you need to complete.
Side Note: All those online achievement can be boosted pretty easily as the online part of this game is not really that active, just get a friend who has the game or head over to the Achievement Trading Thread
and then get your partner to search for your game.