Go to the upper right hand corner and click on the word "Settings". On the next page click on the "Device Manager" on the left hand side. This will bring you to a page which lists all your devices. From this page click on the device you wish to affect. If all of your devices have the same profile,such as "default", give your affected device a different one. Once you have selected a different profile, click on "Edit Device Profiles". Click on the one you wish to change. On this page you can just select the project you want for this machine. Hit save at the end of the page and you should be good to go. Hope this helps.
Cheers