Adding variables to a shell command in Automator
There are multiple ways to solve this problem. One way is already described in the question Automator variable in shell script (make sure to enable the options precisely as follows):


Ask for Finder Items (Type: Folders)
Set Value of Variable (Variable [example]: Directory-Path)
Ask for Text (Checked: Ignore this action's input; Checked: Require an answer)
Set Value of Variable (Variable [example]: Spotify-Url)
Get Value of Variable (Variable: Directory-Path; Checked: Ignore this action's input)
Get Value of Variable (Variable: Spotify-Url)
Run Shell Script (Pass input: as arguments; Content: export PATH=/usr/local/bin:$PATH ; /path/to/spotify-ripper user.name "$1" "$2"—change the "/path/to" part with the real path to spotify-ripper, of course: probably /usr/local/bin/spotify-ripper)


Another way is to use AppleScript, either in a "Run AppleScript" action in Automator or as an AppleScript application saved in AppleScript Editor. Here's an example in AppleScript:

on run
    try
        set spotifyDialog to display dialog "Enter a Spotify URL:" buttons {"Cancel", "OK"} default button "OK" cancel button "Cancel" default answer "https://" with title "Spotify Ripper"
        if the button returned of spotifyDialog is "OK" then
            set spotifyURL to text returned of spotifyDialog
            choose folder with prompt "Choose a folder:"
            set theDirectory to the result
            do shell script "export PATH=/usr/local/bin:$PATH ; /path/to/spotify-ripper user.name " &amp; quoted form of POSIX path of theDirectory &amp; space &amp; spotifyURL
        end if
    end try
end run