Not to be a smart arss but did you read the instruction manual that came with your bow?
If you purchased it used I guess you have an excuse.

Unscrew each limb bolt five turns max before doing the same to the other limb bolt. Continue doing this back and forth until you can see daylight in the little hole on the side of the riser where the limb bolts are located. When the limb bolts are tight you can see the threads of the bolt in this little hole.Do not go past this point because you will do what you did and remove the limbs all together. There will be some tension on the strings but it will be minimal and will allow you to remove and install them.