The default printer is the one selected when the Print dialog opens. If there’s “No printer selected” in the Print dialog, you’ll need to add a new printer.
For most USB printers, all you have to do is update your software and then connect the printer to your Mac. If necessary, macOS automatically detects the printer and downloads any necessary software. For other printers, you may have to complete a few steps to add the printer. Here's how:
- Update your software: Choose Apple menu > App Store, click Updates, then install any software updates listed. Even if no updates appear, this ensures that macOS has the latest information about printer software it can download from Apple. If you don’t do this, you may see a message that software isn’t available when you connect your printer.
- Prepare your printer: Use the instructions that came with your printer to unpack the printer, install ink or toner, and add paper. Turn on the printer and make sure it’s not displaying any errors.
- Connect your printer: Connect the USB cable to your Mac. If you see a message prompting you to download new software, make sure to download and install it.
- Important: If your Mac has a single USB-C port, use a multiport adapter. Connect the printer, then connect a USB-C cable to a power supply to prolong the battery life of your Mac.
- Go to System Preferences, and choose Printers & Scanners.
If a printer appears in the list, you can click on it. If none appears, click the “+” icon To remove a printer, click the “-“ icon.
(This how-to is based on my experiences and info on Apple's support pages — where the images sometimes come from.)