I finally got my 1975 Yamaha DT125B up and running nicely next I want to replace my generator brushes. And help is appreciated .

be GENTLE w/the springs that hold them in and I would suggest the following:
clean the armature with fine sandpaper or emery cloth and the housing with a spray cleaner.  make sure all the connections are clean/secure.
I used Oreilly's chemtool b-12 to spray the housing off and clean it.

Also, look at the brushes.  If they are not close to the wear marker (an engraved line in the brush), I would gentely wipe the end of them w/sandpaper (to allow reseat) and put them back in. 
 

If it's Berryman's B-12...  that's a pretty potent carburetor cleaner.  Nasty stuff.  I'd be careful with it near electrical insulation and plastics.

I cleaned the area up where the points and brushes are just need advice from there. Do you remove the cover that the brushes are stored in or remove them one by one until they are all replaced. Need all advice on brush replacement.

A picture might be helpful...  and there are lots of manuals in the Tech Library...

Anyway, from memory you don't remove anything.  Just carefully pull the spring up and move it to the side and slide the old brush out. Slide new one in move spring back over to hold it.