Once the primary fermentation of your beer is complete, sanitize your secondary fermentation vessel.
Slice the vanilla beans lengthwise and open them up.
Scrape the tar-like interior of the vanilla bean out of the husk and put it and the husk into the bottom of the secondary fermenter.
Rack the beer on top of the vanilla beans before placing the lid and airlock on the secondary fermenter.
Wait 2-4 weeks for the vanilla to extract into the beer. Sampling periodically is fun, but not strictly necessary, as it will be difficult to get too much vanilla in the beer. (This is my opinion, but it might just be because I love vanilla)
2 beans per 5 gal carboyboil honey last 5 min***