[Any advice for accessing Tennogen content?]

I'm using the standalone Warframe launcher, but I'm interested in accessing the Tennogen content
I do have a Steam account and have tried adding Warframe as a 'non-steam game' and launching Warframe through there, but that hasn't worked for me (no Tennogen content was available through the Market or Arsenal, nor through the Steam overlay)
If anyone has other suggestions, or has faced similar problems and resolved them can share advice, it would be greatly appreciated

Thanks in advance :3