The kallisto bus single cell workflow requires two programs: kallisto and bustools

To download and install kallisto go to: https://pachterlab.github.io/kallisto/download

To download and install bustools go to: https://bustools.github.io/download

Pre-built indices, transcript-to-gene maps, transcriptomes, and GTF files for many model organisms are available for download from the kallisto transcriptome indices repository.

A video tutorial for how to install the needed software can be found here.