Going from enlisted to OCS, is this a process where you have to prepare and submit everything yourself?

"prepare and submit everything yourself" for what? - it would help if you gave more information about the topic you are asking about.

Assuming you are asking how to apply to the OCS program, your local Army recruiter is the place to start*. Before you can apply though, you'll need approval from your chain-of-command. The one thing that stands out is that you must be on track to finish a bachelor's degree within one year of enrolling in OCS.

If you don't have a degree, or aren't close to completing one, then Green to Gold* (G2G) is a route you can apply to.

If eligible, OCS will be quicker - classes run throughout the year and it's a 12 week process.
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* https://www.goarmy.com/careers-and-jobs/find-your-path/army-officers/ocs.html
* https://armyrotc.army.mil/green-to-gold/

You need to start with your rnco and talk to your commander. You RNCO should be able to tell you if you qualify or not, and you will need the CO's endorsement to apply. A lot of it will be on you, letters of recommendation as high up as possible, and they used to require an essay on why you want to Commission. I don't know if they do in person boards these days or not.

OCS isn't fun. I didn't find it particularly hard, but TAC Officers aren't Drills and make it a real pain in the ass.

You commenters in the other branches are too easy ha ha! In the Coast Guard going from enlisted to officer means showing that you possess "officer-like qualities". The first of these qualities is the ability to find out what message traffic, manual, or other official directive contains the information and procedures regarding how to apply for OCS. All interservice kidding aside, I wish you the best SGT.