How do I connect two JBL PartyBox 1000 speakers together in stereo (TWS) mode?

Press and hold the TWS button on both speakers simultaneously for 5 seconds until you hear a tone indicating pairing mode, then another tone when the TWS connection is established. Press the L/R button on one speaker to toggle between L channel, R channel, and Stereo — the other speaker will change automatically. By default, the first speaker connected to your device is the primary (L channel) speaker. (Page 14)