If you are the Administrator of your company's account on Ommnio, you can invite as many employees as you want. You must access the web version of Ommnio, click on the "Team" tab, and then on the "Add Employee" button that you will find in the upper right margin.
If, on the other hand, you are an employee and you received an invitation to join Ommnio at some point, you cannot invite new colleagues. You must contact your administrator (probably someone in Human Resources, Communications, or General Management) and ask them to add new employees, if they consider it appropriate.