On this C70, you warm up the bike and shut off the engine. then restart and idle.
Loosen the cam tensioner locknut and lock bolt. (these are a couple inches above the bolt you removed, up there near the kickstarter area)
Slowly loosen the lockbolt until the cam chain becomes quiet and stop. Then retighten the locknut. (the tension is automatically set by that spring).
On some bikes, if the chain is still noisy there is an internal screw you can adjust. That second adjustment screw is inside the area that the spring is. You would remove that bolt that you accidentally took out and stick a scrwedriver up there..
For your particular bike the adjustment proceedure may be different.. Hunt down an owner's manual. This is a normal, schedualed tuneup proceedure so it should be in that manual.