Abide means “to remain with” and God implores us to abide/remain with His love (John 15:9). Since God isn’t a physical being we can be with, we can infer that this is a mental posture. Abiding is keeping our minds with/near/focused on God and His love. It is to be the mental sticking point, the thing our mind goes back to as often as it can, the place where our thoughts linger.
Bonus: this lingering mental focus on God’s love doesn’t need to be laborious, deep, studious, or productive. We can simply enjoy it. Relax. Enjoy “remaining with” God and His love in your thoughts.