Could anyone please tell me how to set the bit-rate to 16?
I assume you want 16-bit WAV? That’s bit depth not bit rate. 
Bit rate is normally used with compressed files, and a good quality MP3 might have a bit rate around 256kbps. Uncompressed WAV files typically have a bit rate about 5 times higher, making the files 5 times larger.
When you [u]export[/u] there is a box for selecting format details.