Low storage on ipad - Apple iPad (16 GB) WiFi Tablet PC

You can delete content in any number of ways. Settings>Geneural>Usage>Storage will show what is taking up all of the space on the iPad. This should help.
6 Tips to Free Up Tons of Storage Space on iPad iPhone and iPod Touch

You will have to remove pictures, videos and apps that you are not using any more. You can sync the ipad to a pc or mac and save the pictures and videos you want.The icloud is tied to your apple id. go to this link ( iCloud ) and sign in with the same info you use to sign in to the app store. The icloud gives you free online storage for pictures videos and documents that you have on the ipad.

It may be too full. Check how much free space you have. Try to have approximately 3GB free. Delete things that are easy to replace like apps, or music you can download again.

the storage is automatically there, you could reset the ipad giving you a fresh start.

Got to settings then general then reset to remove everything and restore the ipad back to factory settings, this would give you the 16gb of storage back for use but also wipe out all the data.

I’m happy to help further over the phone at https://www.6ya.com/expert/jonathan_828b54f422cbefdd

if you have laptop/desktop computer you can sync the iPad with iTunes and download iOS 8.1.2 there:
Upgrading iPad to iOS 8: Through iTunes 1. Backup your iPad
Open iTunes. Select your iPad in iTunes and click Back Up Now.
2. Restart your iPad and your Computer
3. Download and Install the Update
Go to iTunes -> Select iPad -> Check for Update -> Click Download and Update

Whichever method you choose, the process will take quite some time to work depending on how much free storage you have on your iPad, your internet connection, and how Apple's servers are doing with upgrades. Occasionally, Apple will either not let you download the upgrade or it will fail. For iOS 8, you must have an iPad 3 or newer. This does not work with the original iPad - if something goes wrong, restart your device, and try again.

How to Upgrade to iOS 7 on an iPad or iPad Mini
How to Install iOS 8 When Your Device is Low on Storage

see here:
iPhone or iPad Ran Out of Storage Space Heres How to Make Space Available...
How to Free Up Space on an iPhone or iPad

see here:
iPhone or iPad Ran Out of Storage Space Heres How to Make Space Available... How to Free Up Space on an iPhone or iPad

Try turning off the iPad or table then turn it back on of that doesn't work you'll have to bring it to a computer technician.