planning descent on fmc (pmdg 737)

Hi!
So i've put my route into the fmc, put all the airways etc in. I've decided which runway and ILS i want to land on, the problem is how do i find out/know which approach to make? i've tried looking online for charts but i can't work out what means what. Please could someone give me a dumbed down explanation of where and what i should be looking for to decide which approach onto the ILS is best with the route i take.

Thanks!