Im currently working on an project building my own map.
I have all the OSM relevent data on my server, and I want to add an aerial imagery layer to my map.
I know Bing has free aerial imagery data to use, but I dont know how to use it.
That is a question which is not really related to OSM, is it? OSM offers no aerial imagery. I am not sure what you mean by “free”, but according to https://wiki.openstreetmap.org/wiki/Bing their aerial imagery is licensed quite restrictive (e.g. OSM has only the permission to trace from the imagery). You also may find info in https://www.microsoft.com/maps/product/terms.html
In addition to what aseerel4c26 said, what you have to do depends on the tools you use - OpenLayers? Leaflet? The question is really more suited to discussion groups for those particular tools (and they are the better search engine terms to find results).