I have no idea how to update my operating system. Please help me

There are many ways to update an operating system! It really depends on the device you are trying to update. Before you update always make sure you’ve backed up the device to avoid any potential data loss.

iPhone or iOS device:

https://support.apple.com/en-us/HT204204

macOS:

https://support.apple.com/en-us/HT201475 or

https://support.apple.com/en-us/HT204904

watchOS:

https://support.apple.com/en-us/HT204641

Whether you are able to update your iPad to a newer version of iOS/iPadOS will be dictated by your iPad model - and the currently installed version of iOS. You can find this information here:

Settings > General > About

Not sure which iPad you have? Identify your iPad model.

Here is a list of the highest version of iOS supported by the older models of iPad (for simplicity - “generations” are shortened to a number) that are restricted in their ability to be updated:

iPad1 - iOS 5.1.1

iPad2, iPad3 and iPad mini1 - iOS 9.3.5 (WiFi Only models), iOS 9.3.6 (WiFi & Cellular)

iPad4 - iOS 10.3.3 (WiFi Only), iOS 10.3.4 (WiFi & Cellular)

iPad Air1, iPad mini2 and iPad mini3 - iOS 12.5.1

Newer models, not appearing in this list, are all able to be updated to the current version, iPadOS 14.4.

If your iPad is capable of being updated to a more recent version of iOS/iPadOS than is currently installed, these support pages outline both the available methods by which the update can be performed - and troubleshooting should you experience difficulties:

Update your iPhone, iPad or iPod touch – Apple Support

If you can't update or restore your iPhone, iPad or iPod touch – Apple Support

If your iPhone, iPad or iPod touch won’t update - Apple Support

iOS update and restore errors – Apple Support

it's very easy if update is available for you device, read this