To sign in as an administrator for company you are advising, begin by viewing your company list here.
Once you are on the Companies page, press the View button next to the company you wish to sign in for. This will bring you to the company's page shown below, where you can press the Sign In As button in order to sign in as one of the administrator or signatories of the company.
From here you will be able to manage the company as a signatory or admin.
Our full list of help articles can be found here, many of which can help with the managing of a company on our website.
To switch back to your Adviser Account, click Adviser Account under the Switch Account tab at the top right of the screen, shown below.
This will bring you back to the company's adviser page, where you can continue as normal.