The simplest way to do this is to buy a router that is compatible with the broadband adapter. I assume it is a USB thing? These are special router but if you search for 3g/4g broadband router you will find a number options. Read though and be sure you find a EXACT match for the model of adapter you have.
Otherwise if you have a extra machine you can make it into a router using ICS. In this case you have the added issue of using the machines wifi in ADHOC mode which allows other machines to connect to it as though it was a router. This tends to be quite a challenging thing to do if you have never done it. Microsoft has pretty good example on their web site.