If you want federal taxes withheld from your pension then you would need to fill out a W-4p. Here is the link https://www.irs.gov/pub/irs-pdf/fw4p.pdf.
For Ca withholding you would need to file the State version of that form. Here is the link https://edd.ca.gov/siteassets/files/pdf_pub_ctr/de4p.pdf
Once completed just sign them and send them to your pension company and they will start to withhold taxes for you.
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