If you want the module to be available for all users, copy the folder and its contents to

c:\program files\windowspowershell\modules

On some custom installed environments these folders might be called differently. Use

$env:PSModulePath

to see the paths that PowerShell scans for existing modules. Copy the folder to one of the folders listed.

How to install on a machine without an internet connection and load the cmdlets manually

On a computer with an internet connection enter:

Save-Module -Name SharePointPnPPowerShellOnline -Path [c:\foldertosavemoduleto]

In the path specified a folder will be created called SharePointPnPPowerShellOnline. Copy this folder and all its contents to the target computer.

To manually load the cmdlets (notice, this must then be done every time you want to use PnP PowerShell in a PowerShell session) enter:

Import-Module [c:\pathontargetcomputer]\SharePointPnPPowerShellOnline\SharePointPnPPowerShellOnline.psd1 -DisableNameChecking