How to fill "secret" when setting Bitbucket webhook use Bamboo REST API

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Environment :

bitbucket 6.4.0
bamboo 7.0

Goal : 

build bamboo plan using bitbucket webhook

Problem :

In bitbucket, I already set webhook using bamboo REST api,

but when I was triggering test connection, always 40x error because of authentification error.

So I made Personal Access Token in Bamboo, and also testing with curl. It was worked.

>>> curl -X POST -H 'Authorization: Bearer MjcxMTAyNDA1NTU2OoMVVfWJtxxxxxxx' http://localhost:8085/rest/api/1.0/queue/MY-PLAN

But I fiiled that token in bitbucket webhook secret, I didn't work.

So this is my question.

1. Is the correct method that fill the 'secret' input box with Personal Access Token?

2. If 1 is wrong, How do i fill that 'secret' input box?

3. Or is any other suggestion to run bamboo plan with bitbucket repository PR?