Fill in your information with a valid e-mail address, and you will get a demo key that will allow you to try out all the commercial features of the 3CX Phone System. You will also get a link to a nice PDF manual for 3CX, or if you are very security conscious, you can click on the link under the heading Updates, which will take you to the links to download without giving you a demo key. You can also go directly to the following link:
3CX is approximately a 40MB download. You may also want to download the 3CX Assistant and VoIP Phone right away from the same page.