Select location that does not have visible veins. Press a pen cap, tube or syringe cap on that location to leave and imprint.
Swab that location. Wipe vigorously from different directions if there are hairs, to clean hairs from all sides.
Pick up a fold of skin between your fingers. Inject into the end of the fold, needle is parallel to muscles below.
Press on injection side for 10-15 seconds to promote closing-off of any damaged vessels to prevent bleed bruises that can happen from time to time.
It is easier to see and visualize veins on your legs. Some get lumps and do better with belly injections VS legs or other way around.