When adding a new switch the only real issue you may come across is if it has spanning-tree enabled. If it does then you may get an outage for about a minute while the spanning tree sorts itself out. The reason you may ned spanning tree is if you connect any of your switches to more than one other switch, this could lead to loops in the network, that would cause you severe problems if spanning tree is not enabled. If you have not connected switches together like this, then you can probably not bother with spanning tree at all.
Other than that, you may need to configure VLANs, if you use them, and a management IP address if you want to manage the new switch.
Apart from these it should be just a case of plug it in, connect to the rest of the network, and away you go.