Alright here I will describe affinities, not resistances. Affinities are something different. Affinities are a natural 'blessing' of the element on a character. So firstly to explain how to get these. You can get them at character creation. The other way is through a MAJOR event IC that enables you to take the affinity. Do not bug the GM about it though or the GM will probably get pissy and just never let you get one.
So what exactly is an affinity? An affinity is a passive that enables a few things.
*Firstly they allow a +10%[Know] attack that is purely that element damage; for 10STA and 5FP.
-This attack is single target single hit, quick attack, but to make it target upto 3 people increase the cost by 3STA 2FP per person
*An enchantment can be done as well onto a weapon granting is +15%[know] damage of the element for 5 turns for 5STA 7FP
*This also allows passive non stated use of teh element, like uisng fire as a light, or putting out small fires with water.
-If you want to do something big like powering a computer with electric affinity, then you will have to pay FP.