You can now register online and apply for your forest premium in January of each year. Please see links below to a video tutorial of how to apply online and a link to Agfood Online for where to apply.
You may still apply by application form (Form 4) if you prefer but please note your forest premium will be paid in April not January.

Agfood Online Web Page

Video tutorial on how to apply online for the forest premium
http://www.agriculture.gov.ie/agfoodiehelpvideos/applyingforaforestrypremiumonline/

Link to Department website to register and/or apply online
https://agfood.agriculture.gov.ie/ssoauthagfood/individual.jsp