Once you have established how to get a musical sound out of the bass guitar without damaging yourself you need to understand what notes you are playing. Although much of the technique you will learn will revolve around note patterns on the finger board it is important to at least know where you are starting from, if only to agree with other musicians how you are going to play the song. over time you will want to be able to know what note you are playing wherever your left hand falls on the fingerboard but this will take time and so combining this with the knowledge of the patterns that make up chords and scales will help you progress quicker and further with your playing.
On a 4 string bass the thickest string is E, the next is A, followed by D and finally G.
A five string bass usually has a low B string added although sometimes it can have a high C string. A six string bass has both a low B and a high C.