What is the process for security clearance prior to joining the Navy as an officer?

If it's for an SF-86, you'll need the following: All addresses for places you've lived. (last 10 years) You will need a personal reference for each of those address, that is not a family member or roommate. List of employers for the last 10 years (or just the ones past the age of 18)...with a point of contact for each. Same goes for schools. Have info for all family members (mom, dad, spouse, in-laws, siblings) like current address, birthdate, maiden name. Three people that know you well. You will need dates, relationship, explanation of relationship, phone numbers, email, and current address. Any foreign contacts? If so, prepare to fully explain relationship. All foreign travel. Last but not least, be prepared to answer questions truthfully. Drug use, criminal activity, etc. Sorry, there is more, but this is all I can remember.

The form you need is the SF86. If you are getting a clearance you will have a link emailed to you to fill out digitally, but the form is a standard government form that anyone can download. It's a PDF, so work your way through it. If you have it filled out ahead of time, you can use it as a quick reference when the time comes. Best of luck.

You'll need your entire adult history. Dates, places traveled, tickets, drug usage, criminal background and references. Both family and friends. Depending on your level of clearance you will have to do periodic re-investigations, so you'll need to provide the same info every time. They don't like deviations in info.
Good luck.