You have a business, with employees. Those employees know what to do because you have procedures and policies in place to guide them.
One of those policies should be an Acceptable Use Policy which should describe in broad/general terms how the data, information, computing resources and internet access of your business can and cannot be used.
In the last few years the rise of social media, online file storage, smartphones, and tablets has significantly changed how employees can be productive for your business. But this also would cause challenges and threats to the data, resources and productivity your business relies on.
Your business also has to contend with the rise of the BYOD behaviour. This is where employees are bringing their own devices (smartphones, tablets, laptops) to do the work you pay them for.
If your business has an Acceptable Use Policy, you need to review it on a regular basis. If your business doesn’t have an Acceptable Use Policy, then you should have one to protect your business and have your employees read, accept and sign it.
On the Small Business Victoria website is a word document call HR Manual Template. Specifically on pages 4 to 8 of the HR Manual template, which is a Word document that you can download. While this document focuses on minimising the risk of abuse and inappropriate behaviour, there is no reason that I see why you cannot also include statements on how employees can and cannot use the digital information and computing resources that belong to your business.
You can read further about Acceptable Use Policies, here on wikipedia.