Government advice for businesses and employers can be found at https://www.gov.uk/government/publications/guidance-to-employers-and-businesses-about-covid-19
You can read the full text of the Chancellor's speech outlining additional support for businesses, delivered on 18 March at https://www.gov.uk/government/speeches/chancellor-of-the-exchequer-rishi-sunak-on-covid19-response
Details on how to access the different support measures available to businesses will be available in the coming days.