For adding one project to another project solution u follows these steps
step 1--Frist open the project in which u want to add another project in your case open Module project
Step 2--Right click on solution in Solution Explorer and than choose Add-->Choose Existing project than Add Existing project dialog box open
step 3-- In Add Existing project dialog box, u can brawose path for another project which u want to add and choose the project file and click on Ok
Step 4-- Now both project are in your one solution than u will be right click on Class project and build it After that right click on Module Project and add referance of Class project to use in that project.
HOpe u got my point