First aid provision needs to be suitable for the number of people expected to attend the event. And, for the type of event you are putting on.
Make sure that the basic services for first aid are always available. At smaller events a qualified first aider should be present and an area suitable for first aid treatment. This should include a supply of water.
The first aid post should be clearly signposted. Where an ambulance is required, a parking area should be provided. This should be close to the first aid post with clear entrance/exit to the site at all times.
Make sure that all persons working at the event know where the first aid post is, and, where appropriate, the identity of the first aider.
Organisers may wish to refer to the following online resources;