Once the file is uploaded and saved on your computer, you need to upload 2 files via FTP and one file in backend.
1: Download the module and open the folder called: vconnectsystems-am-opencart-dk
2: The two files (marked in red in the picture underneath), needs to be uploaded to FTP
3: Once this is done, FTP will tell you that the files was transferred successfully
Next step is to upload the file: all_in_one.ocmod.xml, to backend.
4: Go to backend > Extension Installer > Upload and choose the file showed on the picture above.
5: After this, find the module in your OpenCart backend via "Modules". Here you can activate the module.
Now the module is ready to be setup. Find a guide for that here: How to setup the module in OpenCart