If you have multiple nozzle sizes or multiple printers, it will be easiest to install separate machine profiles for each printer. Let's install a RostockMAX single extruder profile.

Click here to download the RostockMAX 3MF file we'll use here. (download begins immediately)

Just like before, select "File" and "Open File(s)..."

Navigate to the folder containing the Quick Start .3mf project file for your desired nozzle size and printer type, and click "Open" and "Open as project"

If the shown dialogue box appears, make sure all the drop down menu options are set to "Update Existing", and click "Open"

When the project opens, you'll see the second machine has been added to your list of machines in the upper left, and a new slicing profile has been automatically imported on the right.