To change a bicycle chain, a chain tool is required, which is a device that's used to detach and remove links from a chain. Other items that come in handy during the process include a piece of stiff wire, some chain lubricant and a pair of surgical gloves.
The first step in changing a bike chain is to remove the old chain using the chain tool. Align one of the chain pins in the slot inside of the chain tool, and turn the handle on the tool to nudge the pin until it is almost all of the way out of the chain. The next step is to pull the chain apart so that it forms one long strand.
Before throwing away the old chain, it should be used to determine the right length for the new chain. Hang both chains from nails that are side-by-side on the wall, and grab the new chain at the link that lines up with the last link of the old chain. Use the chain tool to push the pin almost all of the way out of the link that will be the last link of the new chain. Turn the bike on its side and run the chain through the front derailer, over the smallest front and back gears, and then through the back derailer. Finally, push the pin in the last link through the side of the first link to make a complete loop out of the chain.