From your Safe, go to "Apps" and select Request Finance. Sign in, open the invoice you want to pay, click on "Pay", and when prompted for a wallet selection, pick "Safe". If your Safe is configured for multiple signatures, don't forget to tell the other owners to sign as well.

If you encounter any issues using Request Finance with Safe, please refer to Safe's help center and try enabling third-party cookies; see: https://help.safe.global/en/articles/40797-why-do-i-need-to-enable-third-party-cookies-for-safe-apps