If you've been asked to do an Armalytix report by an advisor like your accountant, or a solicitor, then you should have received an email from them, or from Armalytix on their behalf with a link to get started - just click the "Get Started" link to start your report.
If you've never received an email with an Armalytix "Get Started" link then you'll need to speak to the company that has asked you to use Armalytix and check if they have set you up in the system yet - they may need to set you up and send you an invite.