Just tap "prepare" from the main menu.
In the prepare screen, tap "leveling".
Doing this melts any excess plastic in the nozzle, and also ensures that the Kobra Plus's sensors are calibrated correctly. In the past, there were issues with certain models punching the nozzle into the plate, so this sensor test ensures that the printer is reading its inputs correctly.
You could use the flat side of a hex wrench, or the flat side of the included metal wrench. Hold it against the nozzle's point until the printer reads it and moves on.
After the nozzle has been tested, the printer head will return to home. Wait for this to complete.
Allow the printer to preheat for its full test cycle. This can take a few minutes, so go make yourself a sandwich.
Once ready, your Anycubic Kobra Plus 3D printer will begin the process of probing the print plate at pre-defined points to ensure a perfectly level build platform. As long as you've tightened the screws beneath the printer's build plate and on the printer head, this step should go off without a hitch. Wait for the process to complete, and you'll be ready to print!
I recommend repeating this process between major prints, at the least, to ensure that all your projects come out grand.
Interested in this 3D printer? Check out my review on Anycubic's Kobra Plus!