That human update build is not available on the public Main Galaxy instance at http://usegalaxy.org (or in the default included builds in Cloudman). Using hg19 or hg38 instead is the quickest alternative. This one of the few tools in Galaxy that does not support Custom reference genomes from the history.
However - it might accept a Custom build - I have not tested that usage with this tool, but you could. This wiki link below explains how to promote a custom reference genome to a custom build. Once created, assign the build to all of the input datasets as the "database" attribute.
Should that fail, then setting up a local or cloud Galaxy and adding this genome is the solution. Data managers can be used, so all can be done through the user interface as admin on your own Galaxy (there are no special indexes for this particular tool, just the installed/added genome is utilized, but you could add in indexes for other tools if you wanted).
Take care, Jen, Galaxy team