Copy this into a word document, fill in the blanks, print it, sign it, and hand it to your boss.
To (Boss's name)
Thank you for this job opportunity, it has been a great experience for the last 7 years. This letter is to inform you that I'll be resigning from (company name) in 2 weeks to pursue other career opportunities. My last day available at this position will be (insert the date you will work your last shift).
(your signature, and the date you sign it)
(your name, printed)