This script will download the command line tool for Firefox Send that was created by Tim Visée and place it directly into your C:\Windows\System32\ folder so that it is accessible via the command line on your system.

Firefox Send for Windows Command Line.ps1

<#
    Downloads FireFox Send executable made by Tim Visée - https://github.com/timvisee/ffsend/releases
    Current Version ffsend v0.2.30 as of 03-14-19
    Script made by John Davis @John_Davis - https://github.com/Belorum
#>

Net Session 2>&1 > $null

if ( $? -eq "False" ) {
    $Current_Time = Get-Date

    (New-Object System.Net.WebClient).DownloadFile( "https://github.com/timvisee/ffsend/releases/download/v0.2.30/ffsend-v0.2.30-windows-x64.exe", "C:\Windows\System32")

    $PopupWindow = New-Object -ComObject Wscript.Shell
    $PopupWindow.Popup( "Time taken: $(( Get-Date ).Subtract( $Current_Time ).Seconds) second(s)",0,"  Download Complete",0x40 ) | Out-Null
} else {
     $PopupWindow = New-Object -ComObject Wscript.Shell
     $PopupWindow.Popup( "  Unable to download ffsend to `"C:\Windows\System32\`". `n`nPlease run again with Admin rights",0,"  Download Failed",0x10 ) | Out-Null
}