There are lots of different posts; each with its own approach to solving this problem. After trying several, I found the one that worked for me.
1. Remove the BSL from your Macbook's memory. Click on the Bluetooth icon in your menu bar, select BT preferences, highlight the BSL and click the minus sign to remove it. If it's not there, obviously you can skip this step.
2. Shut down iTunes.
3. Turn on the BSL and tap the Bluetooth button to put it in discoverable mode.
4. Click on the Bluetooth icon in your menu bar, select 'Setup Bluetooth device...'
5. Follow the instructions. You should get a message after a few minutes that the device was setup correctly.
6. Open iTunes (or Safari for Pandora, etc.)
7. Click on the Bluetooth icon in your menu bar, highlight the BSL and select 'Use as Audio Device.'
Should work. Now I know that seems pretty simple but the mistake most people make is they don't run the setup wizard. By not doing that, the Macbook will find 'a' device but the configuration changes that need to be made in Lion don't occur. It just sees the device.
Actually the suggestion posted above does work with one exception. I needed to go to the sound preferences and in the first column on the left I needed to select the Bose speakers as my sound output, not the internal speakers. When I started iTunes and selected music the speaker responded. Before that I was told that the speaker was paired but not connected.