Non Profit needs ecommerce

I am new at wordpress. I am doing volunteer work for a non profit that provides transitional housing for homeless veterans (VSCOA.org) what they want to do is add ecommerce to the existing website. they have a deal to sell four brands of coffee. While I have an IT background it wasn’t in webmastering. I am just learning wordpress. anyone have any ideas? I would like to just use a plugin to make a purchasing page and shopping cart while keeping the existing site in tack
Help please