How to create password

Thanks for posting in the Apple Support Communities Moryoon,

We understand you're looking for info on creating an 8 character password.

If you're referring to a device passcode, you can use a four digit, six digit, or alpha-numeric code. The following page explains how: Use a passcode with your iPhone, iPad, or iPod touch

For your Apple ID password, 8 digits including upper and lowercase letter, and at least one number are required, but more can be used if you choose. You can learn more about changing your Apple ID password, here: Change your Apple ID password

We hope this helps!