First, welcome aboard.
1. Make sure your diopter is properly set. LV will help but you don't want to run around holding the camera at arms length trying to manually focus a lens.
2. That lens will only properly work in M mode. In all other modes, it will shoot wide open regardless of where you have the aperture ring set. The green button centers the meter based on that set aperture.
3. Practice on something simple, that does not move. Beware of enlarging images on the LCD as it is a poor tool for judging sharpness.
4. Try Catch in Focus. Set your camera to AF-C, set your exposure, press and hold the shutter release, and turn the focus ring slowly until the camera takes a photo. You will have to turn this feature on in your custom menu.
5. Practice on something simple (yes, I said it twice).
Using manual focus lenses is fun and quite simple once you get the hang of it.
Collection: Manual Focus