Instructions
Start small by introducing the concept of the monkey sitting in your lap. Place the monkey in your lap and say "lap" to indicate the behavior you want. If he stays on your lap the first time give lots of praise and treats to reinforce what it is you want the monkey to do.
Once the monkey is comfortable with sitting on your lap, graduate him to sitting on your forearm by placing him there. Use a command such as "arm" to let the monkey know what you are expecting. Again, lots of treats and praise.
Climbing is one of a monkey's natural abilities. Use this to your advantage by having the monkey sit on your forearm and hold a piece of treat at about your ear level.
Use the command "shoulder" as the monkey climbs from your forearm to get the treat. Having the treat just out of reach of your monkey helps encourage it to climb to your shoulder. Even if he doesn't make it all the way to your shoulder at first, give him the treat anyway to reinforce the act of climbing up there.
How to Shoulder Train a Pet Monkey
Monkeys are a wild species and it may take hours of training to achieve the goal of your pet sitting upon your shoulder. However, with hard work and perseverance your pet monkey will be trained to accompany you while perched on your shoulder.