Before starting to use the Solution Environmental Impact tool, make sure the information you want to communicate is clear: What is the main environmental benefit of your Solution compared to the Mainstream alternative? In which stage(s) of the lifecycle does it occur (production, usage or disposal)?
Once you have identified the answers to those 2 questions, you can start filling the first tab of the tool 00.Scope definition. There you have to define the Functional Unit: what is my solution used for exactly (for example, the functional unit of a lamp bulb can be to light a 50 square meters class room for 8 hours a day for 10 years)? The tool will help you calculate the emissions associated with your solution and for the Mainstream Alternative for that Functional Unit. A detailed step-by-step guide is available on the Submission Page (SEI_User_Guide).