HTTP interface
If the agent is running as a service or a daemon, its web interface should be accessible at http://hostname:62354.
If the machine connecting to this interface is trusted (see httpd-trust configuration directive), a link will be available to force immediate execution.
Command line
NOTE
Don’t use PowerShell as commandline interpreter: it changes some environment context the agent doesn’t handle well.
Open a command interpreter windows (cmd.exe), with administrator privileges (right click, Run as Administrator).
Go to C:\Program files\GLPI-Agent (adapt path depending on your configuration) folder to run it:
cd "C:\Program files\GLPI-Agent"
glpi-agent