Before the actual introduction, take a few days to get both dogs used to the others scent. Rub each dog down well with a hand towel and take that towel and give it to the other dog to sniff & keep for 3 or 4 days. This will get them used to having the other dogs scent around.
Next step is the actual introduction. Do this on neutral territory without any other dogs around. Keep both dogs on a leash and let them approach each other at their own pace. If the shy dog is scared, try ignore the behavior, if you comfort him/her, they will think that they really do have something to fear. Instead, try to get the shy dog to play with you, bring his favorite toy along. After he calms down a bit, go over and pet the calm dog, and speak to both dogs in a calm voice. It may take some time and the dogs may need to spend time playing separately in each others presence for a while before the shy dog is ready to really approach the calm dog.
Let the calm dog approach the shy dog, but be prepared to separate them if you see signs of aggression.
If your ultimate goal is to have both dogs live in the same house, let them have several play dates on neutral territory before moving them in together. Taking them on long walks is also a good idea, as it will teach them to walk and work together as a pack and form a bond.