If you expect the signal to swing between 0 and +5V then set the trigger level to somewhere around 2.5V.
As with input coupling the trigger coupling can usually be set to either AC or DC. Perhaps you have it set to AC and that's why the trigger level marker does not show on the right hand side of the screen.

SINGLE waits for the trigger condition to be met, does an acquisition, displays it on the screen and stops. You have to re-arm the trigger.
NORMAL waits for the trigger condition to be met, does an acquisition, displays on the screen, re-arms the trigger and goes back to waiting.
AUTO is like NORMAL but if the trigger condition is not met within a certain time it does the acquisition anyway, re-arms the trigger and starts again.

You should have some sort of indicator, either as a LED or a screen annunciator telling you if the scope is "trigged" (as with a repetitive waveform like PWM output) or "waiting" (as with something like a monitoring a button press).

I have no experiece with your particular scope and have not looked at the manual but I would highly recommend reading it as even these $200-$400 scopes comes with an enormous amount of functionality. It's just incredible what you can get for less than brand name multimeter costs these days.