There are some stickies at the top of the page that give good info on introductions, both for boars and for sow (you'll want to be sure the pigs are either of the same gender or one of them is neutered prior to introduction to prevent any unplanned babies.) Are these new pigs going to be living together? You'll want to introduce them in a neutral space that neither of them feels territorial about (the last time I did introductions, I did them in the bathtub with towels covering the bottom- worked great, as it was totally neutral and had no corners for anyone to get backed into.) Once they work out their dominance issues, you'll want to make sure that the space they are going to be sharing is cleaned and made as 'new' and scentless as possible. This will avoid any territorial issues (moving a new pig into an existing pig's cage without a thorough cleaning often causes the resident pig to become very defensive of their space, but removing scents even from an existing space with a good cleaning makes it a 'neutral' territory for both pigs.) Hope this helps a bit, and definitely check out the stickies on top of the page for detailed introduction information!