Hi Russ. Welcome to AB.
There are three things you need to accomplish with your fretting hand (besides the obvious one of making music).
1) Reach the most notes possible without having to move your hand. Or to put it another way, you want to minimize the movement of your fretting hand.
2) Comfort. In other words minimize the potential for injury.
3) Reduce the chances of picking up bad habits that may affect your playing later.
The most common approach to achieving these goals is to use the 'standard' one finger per fret hand position. That is use one finger for each fret starting at the nut and working up the neck in groups of four.
For example the first position would look like this.
The next position would look like this.
Understand that not everyone follows this scheme religiously. It's just the best suggestion to start with.
Some people, such as myself, can't comfortably reach four frets on the lower part of the neck. I've modified my fretting hand positions to accomodate my smaller hands. For me the first position is this.
I use my ring and pinkie together on the 3rd fret. My second position is this.
My third position is this.
After the 5th fret I can comfortably reach 4 frets so I try to follow the 'standard' positions from there up the neck.
If at all posible you should try to start using the standard positions and modify them only if you need to and as experience guides you.
Hope this helps some.