How can I sign in on ipad

Set up your iPhone, iPad, or iPod touch

1. Turn on your device. ... 
2. If you have another device on iOS 11 or later, use Quick Start. ... 
3. Activate your device. ... 
4. Set up Face ID or Touch ID and create a passcode. ... 
5. Restore or transfer your information and data. ... 
6. Sign in with your Apple ID. ... 
7. Turn on automatic updates and set up other features.

Sign in with your Apple ID - Apple Support

For more detail:

Set up your iPhone, iPad, or iPod touch - Apple Support