Remove the crib mattress from the crib. If the mattress has not already been lowered to the lowest height, lower it now according to the manufacturer's directions. This is most commonly done by removing an allen bolt at each corner of the mattress support spring, lowering the hinges and replacing the allen bolt.
Remove the four allen bolts from the crib's front panel and one allen bolt on either side of the front panel, near the bottom using the supplied allen wrench. If your crib has a dropside front panel, lift the panel up to the highest position and remove the block brakes, on the front legs underneath the panel, with a phillips-head screwdriver.
Remove the front panel from the crib. A droprail panel must be lowered all the way down before you remove it from its track.
Line up the bolt holes in one of the sidebars with two of the bottom bolt holes from which you removed the bolts to separate the front panel. Insert the bolts through the sidebar and back into the bolt holes. Tighten them in place with the supplied allen wrench. Repeat with the sidebar on the other side of the crib. Lay the mattress back on the support spring.