The amount of assembly required varies depending on the manufacturer. Allow a minimum of 30 minutes to assemble a bike. You'll need a screwdriver, socket set and box wrench or open-end wrench. It's best to remove all the parts from the box and verify you have everything before you begin.
Loosen the bolt and slide the handlebars onto the frame. Adjust the height of the handlebars and tighten the bolt just until it won't move. You'll need to straighten the handlebars after the front tire is on and then tighten the bolt all the way.
Slide the seat post into the bike frame if not already installed. Adjust the height, check that it's straight and then tighten the bolt all the way or close the quick-release lever.
Flip the bike over so it's balancing on the handlebars and seat. Put the front tire on the forks. Install the retention clips on either side of the wheel axle. Thread the axle bolts on each side by hand. If the front wheal is quick-release, just insert the axle in the fork all the way and close the handle.
Straighten the wheel and turn it to make sure is spins freely without rubbing against the brake or forks. Hold one axle bolt with a wrench and use another wrench to tighten the bolt on the other side. Then tighten the bolt you were holding. Attach the reflectors to the wheel spokes with a screwdriver.
Look for the "R" and "L" marking on the pedals designating right and left side. Slide the pedals on the crank arms and tighten the bolts.
Turn the bike right side up. Pull the front brake several times. Lift the bike and spin the front wheel to make sure it spins freely. If it's rubbing, verify that the wheel is straight. If it still rubs, adjust the brake.
Hold the front tire between your legs facing the bike while you turn the handlebars to straighten them. Tighten the bolt holding the handlebars.