Login to your IT Company account. On the dashboard area click on services> My services.
On my services page click on your desired domain.
After clicking on view details button on the next page you may get the option to install Applications
In Your Apps you may see the list on apps you have already installed. If you have not yet installed any app click on Install New button.
You may see a list ofavailable applications. Select the one you required
To install wordpress, click on blogs>wordpress and press install. It may install wordpress on your domain
You can view the file manager of your domain to confirm the wordpress successfully installed on your doamin.