How do I fix a loose nikon lens?

The lens is a kit lens that comes with the Nikon D5300 The Nikon DX VR AF-P 18-55mm 1:3.5-5.6

Take it back where you got it and explain.

What is loose? That is very vague!

Is it the mount? You can tighten up the fasteners that hold the mount flange in place.

Is it the front of the lens? The front of the lens when at 55mm is normally a bit wobbly.

You can send it to Nikon for warranty repair. Hopefully you sent in the warranty card for extended warranty.