Starter not working?

[VBMWMO]

My bike a 1971 75/5 I have had it for about four months this is the first bike I have owned and I know very little about them.

So here is the deal when I push the button to activate the starter nothing happens all I hear is a click. I believe the click is coming from the right side I tried to track it down I do know it is coming from under the gas tank though. Now I believe the battery is all charged up since I just removed it from the charger and the charger light said it was all charged up however like I said I have only had the bike four months and I am not sure how old the battery is. Also all the lights come on when I put the key in, the horn works as does the headlight and turn indicators. I did manage to kick start it after many minutes trying.

So I guess what I am wondering is where should I start with trying to trouble shoot the problem bare in mind I have very limited knowledge of motorcycles I do own the Clymer book so I suppose I could figure out what people are talking about

So please someone help me out