The Add computers from... wizard discovers computers in your environment and adds them to the list in one operation. Pick a source, configure it, watch the discovery run, then decide how the results fit into your existing list.

The wizard works in three steps. First you choose a source and fill in its settings. Different sources need different details: a domain name for Active Directory, a start and end address for an IP range, a host name for Hyper-V. Next, the wizard scans that source and shows the computers it finds. Finally you choose where the discovered names land in your list and what happens when a name is already there. Each source has its own page below that explains its settings.
Choose Computers > Add computers from... from the main menu.
Pick a source from the Import from dropdown:
The panel below the dropdown changes to show the settings for the selected source. Each source has its own page in this section that documents its fields.
Click Next > to start discovery.
The wizard runs the source in the background and adds names to the Found computers tree as they are found. An activity indicator spins while the scan is in progress. You can:
If the scan finishes with zero results, Next > stays disabled. There is nothing to import, so the wizard expects you to go < Back, switch to a different source or change the parameters, and try again. Cancel also works if you want to abandon the operation.
Pick a Target group for the discovered computers:
Then choose how to handle names that are already in the list under Duplicates:
Click Finish to write the discovered computers into your list. Click Cancel at any point to abandon the wizard.