I recently had some issues uploading an ISO file to a datastore using the vCenter web console so decided to use WinSCP to access the datastore and upload it that way.
Download and Install WinSCP
You can download the latest version of the software from here: https://winscp.net/eng/download.php
Enable SSH on ESXI host
The first thing you need to do is enable SSH on one of the ESXi hosts. To do this select the host server from the vCenter inventory.
Click Configure, Services, highlight SSH and click start to start the service.
Connecting from WinSCP
We’re now ready to connect via SCP.
Open the application and enter the details for your host (Note: you will need to use the root account). Make sure you select the File protocol as SCP and the port as 22. Click Login.
Once connected, browse to /vmfs/volumes to see the datastore folders (names redacted). Browse to the datastore’s folder.
If you have a folder to copy to (in this case ISO) browse to it.
On the local side find your file and you should be able to copy the file across (drag and drop).
That’s it. Once copied, close the application and don’t forget to stop the SSH service on the ESXi host before you finish!