As a newbie to the forum and bass guitar, when using TAB what is the best way for knowing the rhythm to play at, is it easier just to have the song playing at the same time and take it from there. Only problem I sometimes find is, some songs it is very hard to make out the bass on top of heavy drums/guitar or even vocals
With most TAB you do not get any indication of the rhythm. Some TABS, however, are written with the note "tails" and the fret number as the note head. These give you the rhythm. But these are not common, unfortunately.
It helps if you have heard the song you're trying to learn. Or, as you said, have it playing and try to follow along with the TAB.