Jsonify fortigate

[m_pahlevanzadeh (Mohsen Pahlevanzadeh)]

I visit the following page:

Fortinet module | Filebeat Reference [8.13] | Elastic

At end of above line, it mentioned to fortinet fields.
My scenario:
I get fortiGate syslog and I can put into elastics. Now I want to jsonify , because I need to search according in kibana.
Question:
How can I assign real fortinet fields to real fields?

UPDATE:
For example : Fortinet Field action is exists. And ECS Field evemt.action exists too. How and Where I assign them togeter?

[m_pahlevanzadeh (Mohsen Pahlevanzadeh)]

You have to write filter with mapping.