How do I update software on iPad?

A little hard to help you when you provide NO information about your iPad.

Here are my questions to you.

What year and model iPad do you have/own?

The “A” model number can be found on the aluminium back of your iPad, in small print, right under the larger bold print “iPad”.

What iOS/iPadOS version is this iPad, currently, running?

What is the rated, internal data storage space/capacity of your iPad model and how much of this free, internal data storage capacity is left inside of your iPad model?

All of that additional info can be found in the Settings app, General settings panel, About.

Please attempt to answer all questions asked.

Thank You.

Go to Settings > General > Software Update to see if an update is available.