After downloading the StickyFooter_UNZIP.zip file, UNZIP it. You can find two files. One is the ReadMe.txt file and other is the module file for Joomla 3.x. Choose the file to install. Installation of incorrect file will give you errors.
- For Joomla 3.x.x install : mod_sticky_footer3.x_vX.x.zip
Go to Extensions > Extension Manager and click on the Upload Package File Tab.
Click on browse to choose the correct installation file and click on "Upload and Install"