Following the diagram that comes with the kit, begin removing parts from the sprues and adding them to the shell. Don't simply break the parts off of the sprue. Use a pair of sprue nippers and a hobby knife as shown in this basic kit assembly primer.
All of the parts are a tight fit and gluing may not even be necessary. Do not force parts into place. If the parts do not slide together, scrape a little paint off of the pieces or from inside the hole with a knife or file. Too much pressure can snap the mounting pins. If you need to glue parts, apply the glue from the back or inside of the shell.