You better have a litre of new brake fluid ready and you will need an assistant (hopefully not wife or girl friend for bleeding purposes

).
Take a pair of needle nose vice grips or similar clamp and clamp off the old flex line in the middle (you called it flexible brake line hose). Remove old line from caliper. Install proper end of new flex line in it's place. Now remove the other end of the old flex hose. Make sure the brake fluid reservoir is topped off. Install top end of new flex hose quickly.
Now open bleeder fitting on caliper and bleed caliper. Keep reservoir full or you will have problems. Becareful not to snap the caliper bleeder screw. Spray a penetrating lube on the bleeder screw the night before.
Do you know how to bleed brakes?