Good morning. You'll want to process the cranberries before using them. I would simmer (cook) them in a small amount of water to soften them, and then use an immersion blender. You have 2 choices when it comes to utilization. Make sure you cool it before any yeast is added, obviously.
1) Pre-fermentation: You'll process the fruit as above, mix with water and honey. Add yeast nutrients. You'll also likely need to adjust the pH. Potassium Carbonate is usually used for this. I'm not sure exactly how much you'll need, maybe google can help. If all else fails, 1 tsp per 3 gallons of mead might work (but it's a shot in the dark). Properly rehydrate your yeast, and pitch. Add more yeast nutrients in a staggered fashion.
2) Post-fermentation: the acid is not a concern if you are adding post fermentation. Make a traditional mead using water and honey, make it a little stronger than you otherwise would, depending on what you want the final gravity to be. I suggest an OG of 1.120 which would be ~3.2 lbs of honey for each gallon of must. Ferment to dry, using yeast nutrients. After 3-4 weeks, transfer to secondary, stabilize, and add the cranberries. Let them "steep" for a couple weeks, then rack off of them. Back-sweeten to taste, proabably at least 1/2 lb of honey per gallon of mead.
Cranberries are awesome but somewhat hard to work with. Consider adding some orange juice and zest as well, it's a nice flavor to go with cranberries.
Ken Schramm has a cranberry mead recipe in his book, the Compleat Meadmaker.