How do you access the cloud?

On a computer you can use an internet browser and log into icloud.com and access many things in iCloud. On an iPhone or other iOS device iCloud is designed to be viewed by using the apps on the device (e.g., the Files app for iCloud Drive, the Photos app for iCloud Photos, the Notes app for notes, etc.).

iCloud.com is not designed for access by a mobile browser but you can force Safari on a mobile device by first attempting to go there and then touch and hold the semicircular refresh icon in the address bar until "Request Desktop Site" appears.

Also note that while you can view synced data as described above, it is not possible to view the contents of an iCloud Backup. You can only use the backup to do a full restore of a device or to setup a new device.