Norah, really no need for formal, detailed instructions, eye ball your soap:water mix depending on how strong you think you want it, add it to the mixing cup but don't fill it to the brim, connect the foam gun to the hose and use the brass slider to regulate the amount of foamy mix you want according to the ounces per gallon chart right on the bottle ( you really don't have to depend on that once you start using it often). Flip the slider to alternate between flowing foamy solution and plain water.
I highly recommend anyone to get a plastic cut off switch with quick disconnects to attach to the hose for the foam gun to attach to. This way you can completely control the water flow through the hose and very quickly remove and reinstall the foam gun or switch to a nozzle. Sears is probably the best bet for one stop shopping for these items although I did get my plastic Gilmour cut off switches at Lowe's