how to delete a partition

Here is the article on using Disk Utility to work with partitions. Note the information at the beginning of the article: if this is for Windows, you need to use Boot Camp Assistant instead.

Partition a physical disk in Disk Utility on Mac - Apple Support

You can select your macOS version at the top.

Use Disk Utility.app

Here you can select your drive and click the Partition button. From here you can see the partitions on the drive, as well as create and delete them.

Does the User actually mean a Volume versus Partition

Use more than one version of macOS on a Mac