How do I get all my stuff from my iPhone to my iPad?

If you mean you iCloud data, just sign into the same iCloud account on your iPad in Settings>iCloud and turn the data you want to sync to On.

If you want all the data and settings on your iPhone to be transferred to your iPad, restore your iPad to the backup of your iPhone. There are some limitations to this type of "cross-device" restoring to be aware of:

1. Photos and videos in the camera roll on your iPhone will not be restored to your iPad. These would have to be imported to your computer and synced to your iPad.
2. Only third-party apps will be restored to the iPad (not apps that are pre-installed on your iPhone).
3. Only apps that are compatible with your iPad would be restored to your iPad.

Also, as in all cases when you restore to a backup, your iPad would have to be running the same or higher version of iOS as your iPhone in order to restore the backup.