You can always refer to the installation manual...
Or just repeat the installation process in reverse order.
Get it from the manufacturer's website.
Or hit Google.
It is logically not possible that the manufacturer's website does not have a PDF download for the manual. I don't know what the actual structure of the cooler is, so I don't want to speculate anything on my own.
Click on the words "User Manual" and download the zipped folder.
The fan is held on with rubber fan posts that stick out of the top and bottom of the heat sink. To remove the fan all you should need do is grab the top of the post and pull it away from the heatsink. You may have to remove the heat sink from the motherboard to have easy access to all the posts.