Congratulations on joining the gym. I wish you all the success in achieving your personal goal. I never had a personal trainer when I started but I had a few friends and guys who were a part of the gym show me the 'ropes' for a few sessions. This worked and I also did alot of reading of body building and fitness magazines to obtain more knoweledge in doing the correct excercises and other useful tips.
But here are my tips on getting the 15 pounds of muscle added:
1. Don't over train. I know it will seem as though that the more you do the
more you will gain but that is not the case. Your body needs rest in order
for it to grow. So limit your training to no more than 5 times a week an 1hr
a session. Remember staying in the gym longer won't do any good either
based on the law of deminishing returns.
2. Don't watch what others are doing. Go at your own pace and try not to
injur your self by lifting too heavy. If you want to go heavy be sure to get
someone to assist you.
3. Get some sleep. This is necessary for the body to repair your muscle
4. Most important you need to eat well. Eat at least 4-5 times a day to help
feed the muscles and to keep your metabolism up. Good muscle building
foods I would recommend to you are raw almonds (with the skin), whey
protein, extra virgin olive oil, spinich, natural peanut butter, chicken breast
oats, seeds (pumkin seeds, flax seeds, sunflower seeds), non fat or low
fat cottage cheese, whole grain rice and bread, low or non fat yogurt, oats,
skim or low fat milk, seamoss, eggs and friuts and vegetables and remember to drink lots of water.
5. I would recommend that you try to eat before goint to gym at least an 1hr
before in order to have energy and eat after you excercise in order to repair muscles.
Good luck and have fun building your 15 pounds