Step 1: After you've downloaded the latest version of Magecredit (it should be a ZIP file), unzip the file's contents to a local directory on your computer.
Step 2: Next, copy over all the files associatively (to the same directories) in your Magento installation. You can use FTP to do this remotely if your files are on a server.
Step 3: Log into your Magento admin panel (log out and log back in if you're already logged in), clear cache and you should see a notification come up telling you that Magecredit has been successfully installed. Yay!
Please read our One Step Checkout guide as store credit options may not show up in your payment options if the Magento base templates are not being used.