I am keeping a yearling for a friend as a favor, she's a bit scrawny and we are trying to figure out the best nutrition for her. He didn't have much grass at his place but I have 12 acres and only two horses so there is plenty for her now. Does anyone have suggestions on what percent protein and fat I should look for in a feed, or a specific feed to try in general? I feed my mare Tribute Kalm N Ez but the yearling won't touch pellets. Also, if there's a protein lick you suggest as well please let me know!

I have been feeding my filly Tribute Growth Textured. I bought her at 3 months and literally pull her from mom the day I took her ( mom didn't have much milk and was malnourished). She will be a year old in June. 
I feed half scoop of Grain 2x a day, has access to EquiLix tub, alfalfa hay and lush pasture. She looks fantastic!

I have been extremely pleased with Bluebonnet either the Horseman's Elite Mare and Foal or the Intensify Growth & Development.My now 2 year old has been on their feed since before she was born and she's really awesome looking. She looks better than some of the now three year olds that were just on an all stock mix and fescue pastures (they did get bermuda hay) when I bought them as long yearlings. All the way around she's more developed. They will catch up but it's definitely given her a boost. 

I feed Purina Ultium Growth. I start my mares on it a couple of months before they foal, and they stay on it until they're 2. I do have a lot of grass, though. I don't feed hay. 

I got her in March, she turned 1 in February.  I have been feeding Ultium Growth, alfalfa, and Horse Guard and she's out on pasture.  I just added Renew Gold.  She's very shiny and in great weight.  I"m playing with the ratios a little bit right now because she hit a huge growth spurt and I want to make sure her feed is keeping up with her.

Total protein needs to be a little over 15% for the entire diet. That is pasture, hay and any feed that you might add. Calcium and Phos need to be balanced. A grass hay pasture with some added alfalfa to provide some additional protein and Renew Gold will hit your numbers and Cal / Phos easily. If you feed grain based feed, you will likely need additional calcium. Clean water, salt and you would be good to go. Over feeding of protein or Calcium can encourage developmental issues. Balance is the key in growing to potential without overgrowing.