How do I adjust V-brakes as the pads wear?

The rim brakes on my last bike had a barrel adjuster that did what you ask. My new bike has disk brakes and they self-adjust.

The barrel adjuster here is the black cylinder on the right-side. The brake housing/cable pass through the middle. To bring the pads closer to the rim, rotate the barrel adjuster so it comes out from the lever's body by a turn or two, and then tighten the thinner lock ring in the opposite direction against the body. Check the rim still rotates freely between the pads.