Noob in need of advice PLEASE


Ok to sum it up, Ive got the zte merit z990g. Somewhere along rooting & installing a custom rom I messed up. Kids erased whole sd card containing my backup so I had to ask for a nandroid recovery. Now that Ive obtained it, I've got a question:

Seeing as its a .rar file, I was told to "un-rar it and place it in right destionation on phones sd and install it. My question for those who can offer assistance (preferrably some by one with proper knowledge in this device area) is : How do I exactly "un-rar a file and does it need to be placed at the root of my sd card? After un-raring it, do I rename it or convert to a zip or something?

As you can see, Im lost here. Could someone please explain what needs to be done so I can install this nandroid stock recovery to my device?

Thank you in advance