Installing a new chainEdit
In general a new chain comes with detailed mounting instructions. For Shimano 8 speed or more , chain can be shipped :
- With a preinstalled pin , that can be used to close the chain
- Without preinstalled pin, but with a special reinforced connecting pin
Important is for Shimano, and probably for many modern chains, to DO NOT reuse ordinary pins . It is explained here :  On modern Shimano chains you should push the original rivet out entirely and replace it with a special replacement rivet, reinstalling the original pin is likely to cause the chain to break at that point.
It’s important to buy the right type of chain for your bike. If you ride a geared bike then a multi-speed chain that is compatible with your drive train is the correct choice. It’s also important to make sure your chain is compatible with the brand of components you are using.