If the slack line didn't twist when you lowered the rod, just resume reeling. Fill a spincast reel the same way you do a spinning reel. Don't forget to thread the line through the hole in the reel face before you tie it to the spool. Spincasting reels don't hold very much line as a rule, so make sure to open it up and check it frequently. A good premium line like Berkley fishing line will last a long time.
Some professional fishermen change their line everyday, but that is in extreme cases.
Make sure you store your reels in a cool place and keep them out of direct sunlight. Heat and sunlight are enemies of line that will weaken it, but with proper care and spooling, you should have tangle-free fishing. Now that you have new line on your rods take a closer look at your tackle box and your hooks. Hook gap is overlooked by many anglers as something that is not that important, but if you want to catch more fish this season you should pay attention to this little detail. Hook gap is the distance between the hook shank and the point of the hook.