You can apply for Planning Permission online through the Planning Portal. You will need to register. The Planning Portal has produced a best practice guide called Maps, Plans and Planning Applications: What to submit (.pdf 510KB) which you may find useful.
Every planning application needs a site location plan and block plan showing the location and boundaries of the site you are planning to work on. You can use the Planning Portal's 'Buy a Plan' service to ensure that you meet the requirements, whether you are a planning professional or first-time applicant.
Alternatively, you can print out the relevant Application Form(s) from this page (please note that these forms cannot be completed online).
Downloads: