IMPORTANT NOTE :
If you try to import a configuration file into the Running Configuration (the current one), it will fail.)

What you need to do is import from a configuration file to the startup configuration file as a destination and then reboot.

Go into Administration then click File Management to expand, then click File Operations to open its pane.
Now select
Operation Type : Update File
Destination File Type : Startup Configuration
Copy Method : HTTP/HTTPS
Then click Choose File and a new window will pop up.
In the Choose File window point to the downloaded configuration file location, select it and click Open.
Then click Apply for it to load your configuration file into the STARTUP CONFIG.
The switch will send a notification that the operation has been completed.
You must now restart the switch for the changes to apply.
Click Administration > Reboot
Select Immediate and click on Reboot button.
Note that the device might take some time to reboot.