How do l upload my pictures and videos from my iPad to iCloud so I can free up space on my iPad?

See the information in Set up and use iCloud Photos - Apple Support including the following from that support article:

iCloud Photos keeps all your photos and videos in their original, high-resolution version. To save storage space on your device, you can turn on Optimize Storage.

If you turn on Optimize Storage, iCloud Photos automatically manages the size of your library on your device. Your original photos and videos are stored in iCloud and space-saving versions are kept on your device. Your library is optimized only when you need space, starting with the photos and videos you access least. You can download the original photos and videos over Wi-Fi or cellular when you need them.

and: Manage your photo and video storage - Apple Support

Note that the storage is managed automatically and the photos will still be on your iPad but some of all of them may be smaller space-saving versions.

iCloud Photos is a syncing service. Any photo you delete from a device where iCloud Photos is turned on will also be deleted from iCloud and from any other device connected to iCloud Photos. You can potentially reduce the storage space required on a device by turning on Optimize Storage.

Apple does not currently offer cloud-only storage for photos. If that is what you want or need, you may want to explore 3rd party options such as Google Photos or Dropbox.

If you want to turn off iCloud Photos on a device, see the information in: https://support.apple.com/en-us/HT204570

I suggest that you save your important photos and videos to your computer rather than iCloud, which is a synching service. If you happen to accidentally delete a photo from one device it will be deleted from all devices. Check this link...

Transfer photos and videos from your iPhone, iPad, or iPod touch - Apple Support