Details
Installation instructions are from here: https://andyinthecloud.com/2013/07/07/new-tool-declarative-rollups-for-lookups/
When entering the URL - be sure to enter the correct instance where the "xxxx" are. eg URL, https://dlrs.xxxx.visual.force.com An example might be https://dlrs.cs31.visual.force.com
Setup
Documentation
Notes
Questions