In modern Windows versions (1809+), simply running Add-AppxPackage as Administrator stages the package. However, to ensure it is provisioned (available for future users), you should use the Add-AppxProvisionedPackage cmdlet (see Method 2 below), which is the technically correct way for "All Users" deployment.
# Install certificate to Trusted Root store (machine-wide) Import-Certificate -FilePath ".\yourApp.cer" -CertStoreLocation "Cert:\LocalMachine\Root" install msix powershell all users