how to use subfolder in c# project

i have created a simple window appllication project now i wan to put the folder name as newfiles which contains c# classes then i wan to use that folder in my project but when ever i accesss that folder it dosent appears it giving error i tried like this

[Using newfiles;

namespace newfiles]

i m getting error on these lines i just wan to know how can i acces those files which are in the newfiles folder

any help plz thx in advance!!!