You may need to charge your Bangle.js first. Use the supplied USB cable and attach it so that with the Bangle's screen facing you, the cable exits to the right.
Bangle.js has one button on the right hand side. Press it to start Bangle.js, and a welcome screen will appear giving you more instructions.
Check out the Bangle.js Wiki for more information and frequently asked questions.
Disclaimer: Under no circumstance shall Pur3 Ltd be liable to a Company or any other Person for any loss of profits, loss of use, or for any damage suffered or costs and expenses incurred by Company or any Person, of any nature or from any cause whatsoever, whether direct, special, incidental or consequential, arising out of or related to the use of Bangle.js.