Need to know how to make one box auto tick, when another is ticked

Do you want the user to be able to untick those boxes, if they wanted to, even if the first ones are ticked?

Should these boxes untick automatically, when the first ones are unticked?

If the answers to these questions are No and Yes (resp.) then just give the fields the same name and export value, and it will work automatically, without needing any scripts.

There are a couple of ways to do this, depends on what you need, but here is basic script to check another checkbox if one is checked, as 'Mouse UP' action of Check Box64 add this script:
if(event.target.value !== "Off")
this.getField("Check Box66").checkThisBox(0, true);