well a very short example is this:
# define the url/adress of your librenms server ( leave /api/v0/ intact)
$baseurl = "http://librenms.lol/api/v0/"
#fill in api token which you can retrieve from web interface
$token = "your api token"
# generating header(do not touch)
$header = @{
"X-Auth-Token" = $token}
#defining url to get devices
$gdevices = $baseurl + "devices?type=network"
#invoking api request and showing results in grid view
Invoke-RestMethod -uri $gdevices -Headers $header |select -ExpandProperty devices -ExcludeProperty sysDescr |ogv
As Aauvinet found out below: the invoke-restmethod command is not available in powershell 2 or below. please installl windows Management framework 5 (which includes a newer version of powershell) or above to work around this .