This can be done in one of two ways. The simplest is to combine copper and tin ingots together in the standard crafting table (or inventory crafting grid). This produces one bronze ingot (as of Public Beta 25) for every pair of copper and tin.
A slightly better way is by alloying the ingots - or their ore variants - together in a forge. If alloying the two ores together, this saves coal that would otherwise have been used in smelting the individual ingots, and unlike crafting them togethor, this method yeilds two ingots rather then one.
As with other ingots, tin can be crafted into a mineral block for compact storage or decorative purposes. While in this form, tin blocks can be used as a beacon base.