According to Helms you need both 303-1419 Remover and 303-1252/2 Tool, Stretchy Belt Installer.No tensioner on the AC belt... it require a stretch belt install / remove tool. Do not install with force it will damage the belt.
Stretch belt tool is not that expensive. <40$ on amazon.
Is this for real? [facepalm]
Edit: Maybe the Lisle 59370 will work. There was a comment that said it worked on 2013 Focus.