Chainsaw chains are available in 3 variations, namely: cutter type, chain sequence, and special additions. The cutter type is also available in 3 types which are the chipper, semi-chisel, and chisel. So if you want to know how to replace a chainsaw chain, you must also know the type of chain you’ll need. 
Easy steps on replacing the chainsaw chain:
Remove the side cover of the chainsaw using a socket wrench or any wrench that could fit into the steel nuts.
Pull back the chainsaw bar backward to loosen the hold of the chain.
Remove the chain and check the chainsaw bar for any damages or if oil is properly lubricating the chain.
Clean the sprocket for any debris.
Install and align the new chain into the groove of the chainsaw bar while making sure that the cutters of the chain are facing forward. You should also remember that the chainsaw direction of the chain is always going on a clockwise turn. 
Replace the side cover and tighten the nuts by hand. Do not over-tighten the nuts at this point using the wrench.
When the side cover is in place, adjust the tension screw using a flat screwdriver. Since you have learned already how to tighten a chainsaw chain, this is now the time you should apply the proper tensioning process.
When the proper tension of the chain is achieved, make pull and push movements with the chain to check if the chain is moving or rotating freely onto the groove of the chainsaw bar.
You can now tighten the screws of the side cover with your wrench.