The free licence allows for just one employee in the tax year. It was introduced for the 2019 to aid single-employee companies with their PAYE Modernisation duties. The one employee limit covers the entire tax year, and is used up even if that employee leaves employment.
Free licence customers are not entitled to support via phone – if you require phone support, please consider a Standard Licence.
If your BrightPay trial has expired, then when you launch BrightPay it will ask for a licence key – simply type or paste in your Free Licence key.
If your trial has not ended, then the licence screen can be accessed from the Upgrade Licence button on the welcome screen or from Help → Licence after opening an employer file.