First what you did wrong. You would not break the line anywhere along the route, as you discovered fliud will come out. to get the fork off you would unbolt the caliper from the leg, leaving it attached to the line.
Now that you have broken the line, you must back up and regroup. The MC should have a level line in it. Remove the rubber diaphragm to see it, fill to the line, replace the rubber and the cap.
By breaking the line you have allowed air into the system. You need to do a standard bleeding operation per the manual. Remov the cap and diaphragm. Pump the lever twice, loosen the bleeder valve at the caliper. YOu'll feel the lever get closer to the grip, close the valve. Release the lever and pump again slowly. Fast pumps and releases will cause a squirt of fluid to jump out. Bad on paint. Cover your tank with a towel.
Rinse and repeat. You can put a hose (clear is nice) on the bleeder valve to contain the mess and watch for air bubbles to come out. Refill the reservoir as needed.