posting to categories by email

I am setting up my Dad’s blog for him and have set up to post by email which he has already done successfully numerous times, now he would to set up categories and post to them…I have already set up the categories, now I just need to know how to post by email directly to them….I have seen some of the other topics here that cover this, but frankly it’s all greek to me…is there a simple answer to this, or is everyone expected to be a programmer (which I am totally not)…because it seems like a lot of the help found here is quite technical and over my head….thanks in advance for any and all help with this !!