You can add and change your company details on the system at any time. Simply click on the Admin tab at the top of your system and this will take you to your Company Details page. Make any changes you need to here and press the Save button.
The majority of the documentation on the system uses the details from your branch on the system (which may differ in name and address from the owning company), so next click on the Branches link in the Company Menu on the right. This takes you to a list of the branches set-up on your system. Click on Edit against against the relevant branch and then make the same changes needed - then click on Save.