Find a local club you like and start helping. There is usually a shortage of people to put away the chairs and collect the glasses at the end of the evening. You are likely to progress to regular floor spots and MCing. They may even ask you to join committee. learn the difference between playing a festival and a folk club.
Find a sing around you like and join in. Be a good audience. Sing appropriate stuff. There is too much self penned teenage angst songs for most audiences.
Join a barn dance band and really learn how to play for others.
Have a repetoire of at least 20 that include 1/3 that others will know. Offer at least 5 variations. eg. With / without instrument etc.
Then you are ready to go on You tube etc.
FloraG.