You can add extra functionality to your SMF forum by installing Mod's to your forum. These Mod's are packages that can change your forum's operation, add features, remove features, and a lot of other possibilities.

These packages can be downloaded from the SMF "Mod Site". Once you have downloaded the required package you need to login to the Admin section of your SMF forum and navigate to
Admin > Packages > Download Packages

Once you are one on Download Packages page, click the "Browse" button at the bottom of the page, navigate to the package you've already downloaded to your local computer and click upload. Once it's uploaded you'll see a confirmation page.



To apply the package, you'll just have to click on "[ Apply Mod ]" in front of the package you've just uploaded, the package is now installed and ready to use.

Note: It is also advisable to carefully read any notes or documentation included with the particular package.