A statement of purpose or SOP is a very crucial part of a college application form. It can make or break your admission chances to many prestigious universities!
Even engineering students need to submit an SOP with their applications wherein they should include all their past education & experiences along with their GRE scores.
Start with a short introduction about yourself, and describe your academic background as well as achievements.
Next you must include why you want to study engineering or how will the course help you. For eg, it may be due to better career prospects.
You can also include where you see yourself in the next five years. For eg, you may see yourself as a consulting manager.
You should explain how studying a particular specialisation or even in a particular university will help you.