My toilet stinks!

[ActuariallySpeaking]

Just one toilet (out of two in our house)
It seems to be coming from the back of the toilet. I think it may be the water overflow tube having some stinky bacteria (well- that's my simplest solution- so I'm starting with that)
I read you can add a cup of bleach into the overflow tube and it should solve the problem. Now... at the risk of sounding like an idiot... What is the water overflow tube on this toilet? It's got one of those fancy button flushers on the top, and the thing with the blue knob releases the water to refill the tank. So... I would think the overflow tube would be under the blue and white buttons? But I'm not sure and I don't want to try getting it off if that's not right...

 

[user 4883]

The water in the tank should be clear. Flush the toilet and hold the handle down and see what color the refill water is. Might have to hold it down until it runs clear. Use a toilet tank bleach tablet to take care of the smell.