Get your sow calm first or he won't feel safe. Couples are known to call for each other when apart.
Get your boar out of the pen. Mine is particularly suborn so I had to hold the sow first. If you don't have a sow and your boar isn't comfortable but you have another guinea pig then hold the other one first so the other knows you mean know harm.
Hold your boar against you supporting it front and rear legs. Do this while transporting to pen or enclosed area.
Place in closed area. ( my boar is big so I have to make sure he doesn't climb the fencing)
Slow and calmly pet your boar so you establish its trust. It took me a while to do this so don't expect to have him right under your hand when you reach in. Guinea pigs are very frightful creatures and scurry away when they sense unfamiliar ness.
Let the boar learn your sent. Once he gets to knowing you he will recognize you so he won't run away as much.
Hold your boar carefully in your lap. Remember to not keep your sow or other pigs waiting for they don't like to be apart for long periods of time.