I’m not sure what I’m missing from your question… Once you’ve gone through the retargeting process matching the bones from the original (ie. prototype characters) to the default Epic blue guy that should be it besides right clicking on the animation you want to assign as I’ve illustrated above. You’re right about “there’s no ‘go’ button” after the retarget process, which threw me the first time I went through the retargeting process. -Then follow the steps at the bottom of this page: