Philodendron care is pretty much universal ..Here is what I can tell you.
1) About watering: They like well drained soil. You can try starting with regular potting soil and add perlite to make sure the water runs easily thru the soil.
...Water when the soil feels dry-ish to the touch, but not dried out completely.
2) Sunlight: They like Medium to bright indirect light.
3) The yellowing: The leaf looks a bit varigated to me. Is there a possibly that there are 2 varieties in the one pot? Otherwise, may I ask..how is it doing now??