Prerequistes:
1) Install DotShoppingCart OpenSource Edition
Install DotShoppingCart Addon:
1) Unzip files to the local directory and copy all files (including sub directories) from Web directory to DotShoppingCart Web directory.
2) Configure Checkout Page to use OnePageCheckout & Anonymous Checkout
3) If you are running on the live site, go to page <your site url>/Admin/Site/License.aspx and install the license key.