I need help going to the next level

I am a 46 yr old woman who has recently lost 44 pounds, and have been using a Karen Voight video alternating working abs one day, upper body the next for six months.  I also have gone from walking to running three miles a day.  I can see results, big time, and am happy about that, but though I am now thin and getting firmer, I would like to see my body look more defined and sculpted.  I am learning to maintain my weight, but am unsure of my nutritional needs for building more muscle.  Can you offer insights on these concerns?