Where is it tangled? In the derailer? I would use a chain tool to split the chain open, and then pull it out, reroute it back to where it should be, then connect the ends back together. I use the Park brand chain tool, as it has a bigger lever and handle than the cheaper smaller ones.
But you should figure out why the chain got tangled, or else it will happen again. Were you shifting when it happened?
Take a pic before you remove the chain, and post it here.