While heavily deprecated and frowned upon, sometimes you'd still need to use the SMB1 protocol in Windows 10. You can effortless enable this through the GUI (Control Panel → Add/Remove Programs), it may be necessary to install it through scripting (e.g. for automated install). One of the methods is through Powershell.

Enabling the SMB1 client but not the server (or vice versa) is a multi-step process, as it's not possible to "only" enable the SMB1 client. First, you need to enable everything of SMB1, then disable the unneeded sub-features. An important item to disable is the SMB1 Deprecation option, as leaving this enabling could result in the automatic removal of all SMB1 features.

Enable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol -NoRestart
Disable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol-Deprecation -NoRestart
Disable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol-Server -NoRestart
Restart-Computer # you can leave this out if you have other stuff to do

Note that you will need to reboot for the changes to take effect but to avoid rebooting multiple times, we only do this at the end of the process.