The En-ROADS User Guide can be found here. The User Guide provides background on the dynamics of En-ROADS, tips for using the simulator, general descriptions, real-world examples, slider settings, and model structure notes for the different sliders in En-ROADS.
Within the simulator, the User Guide section for each slider can also be accessed by clicking the three dots next to the slider, which opens the advanced settings (see screenshot below). Then click the i icon on the right-hand side, which will open the User Guide section for that slider.
In addition to this User Guide, there is an extensive Reference Guide that covers model assumptions and structure, as well as references for data sources.