Is there a simple guide for using Lightning Network?

I'm a bit confused with channels.

If I open a channel and fund it with 1 BTC, and I connect it to another channel. I receive 5 bitcoins through those channels.

If I want to convert that Lightning BTC back to regular BTC, how would I go about that? Is there any way I can keep the channel open with my 6 BTC, and just withdraw 2 BTC or do I need to close the whole channel then re-open?