This is a 1/76 (OO) scale model of a petrol-driven inspection car built for the NER in the early 20th century. Later taken over by LNER

Paint baseplate, cross walls and body (inside and out) using acrylic paints.Glue bits of transparent sheets (OHP foil) to put glass in windows. Glue body to baseplate, insert cross walls at either end. Add people if desired. Paint and attach roof.
Glue one side of chassis to one edge of the base plate. When set, insert 00 scale wheels (e.g. from AliExpress) and glue other side of chassis to baseplate ensuring that wheels rotate freely but don't fall out.