That’s lovely news!
Its a shame they don’t offer dating but not all centres do. It just means you need a back up plan in case the bonding fails - either of returning the new piggy to the centre, or having two cages so they can live separately but as neighbours.
You need to carry out a bonding in neutral territory bonding pen. Please DO NOT put the new piggy directly into the cage of your existing piggy. This will be seen as a territory invasion and could cause a fight.
Ensure the cage they are to live in once bonded is big enough - that is 180x60cm for a boar pair. The bonding pen will also need to be this size or bigger.
You need to put them somewhere your current piggy does not see as his own space to bond them. You then leave them in this space for as several hours to see if they get on. Do not put any hides in the bonding pen, just a pile of hay and some water. If they do get on after several hours, then you need to thoroughly clean out the cage they are to live in so the original piggy does not see it as his own space. You can then move them both to the cage to continue their relationship. During this time you will see a lot of dominance.
It takes around two weeks for the full process to complete. Do not separate them at all unless there are clear signs of failure or fights. If you separate them, then you interrupt the process and when you try to reintroduce them they will need to start back at the beginning.
If they fight, then the bonding has failed and they will need to be immediately separated (safely - use gloves, dnot put your hands in otherwise you cpipd get hurt) and will then need to live apart.
You will need to ensure the hides you have in the cage have two exits (so no piggy can get trapped in a space with no way out as this is how defensive injuries and fights can occur). You also need to ensure you have two of every item so that they do not have to share - two bottles etc. It can be advisable to not use bowls for teenage boars - simply scatter feed veg and pellets by throwing it loose in the cage. This serves two purposes - the dominant piggy will not be able to hog food and prevent the other from getting any, but it is also a great form of enrichment and enables them to forage about and keep occupied. If you do use food bowls, ensure they are put at least a body length apart.
As you don’t know whether the two piggies will be compatible, you will need a plan b for living arrangements in the case the bonding fails. Unfortunately there is a risk with any on spec bonding that it may not work out. As the new piggy is a teenager, then hormones are in play which can make bonding more tricky. It’s always best to prepare for failure but hope for the best.
Please read the guides below before you start bonding. The first guide explains the process. The second guide explains dominance behaviours. These two are important so that you know how to do a bonding but also so that you don’t inadvertently intervene unnecessarily and interrrupt a bonding
Bonding and Interaction: Illustrated social behaviours and bonding dynamics
Dominance Behaviours In Guinea Pigs
A Comprehensive Guide to Guinea Pig Boars