How do I sync my iPad to my iphone

For most purposes do as QuickTimeKirk suggests and sign into iCloud on both devices. You need to set up the services you want to sync. Some things such as music will require you subscribe to Apple Music or Match if you want to sync via iCloud.

Sign in with your Apple ID - https://support.apple.com/HT204053 - Mac and iOS

Set up iCloud on your iPhone, iPad, or iPod touch - https://support.apple.com/HT208681

The other general way to sync everything on them both is to sync them to the same computer. Click on this link -->

Sync your iPhone, iPad, or iPod using your computer - https://support.apple.com/HT201253

Directs you to the iTunes method page for Mojave and earlier, or the Finder method page for Catalina and later.

Sign in to iCloud on both devices.