To withdraw a security issued via STOKR from Bitfinex Securities you need a verified STOKR account and an AMP ID registered with STOKR.
Securities issued via STOKR are Transfer-Restricted Assets on the Liquid Network: they can only be held by AMP wallets whitelisted for that security. Once your AMP ID is whitelisted for the security, you are able to withdraw.
For the full process, see How to withdraw digital securities from Bitfinex Securities.