If you need to upload an ISO to utilise, and mount on a server, you can do this within vSphere.
You will first need to navigate to the "configuration" tab, and then select Storage in the left menu.
Right click on the datastore you'd like to upload to, and select "Browse Datastore".
You will then be able to see an such as below, and click it in order to open the menu, and choose to upload a file.
On that page, browse to the ISO you wish to upload, and then click Open, and you will see a new window popout to show it's uploading.
Once the upload is done, you will then be able to utilise the ISO within your virtual machines.