Alright so let's get creative.
My first reaction very much depends on the manner in which I would learn about my Omnipotence. If I simply wake up and know I'm Omnipotent, then my first reaction is likely going to be "Outstanding!", followed by "How did this happen?" and "Are there others like me?".
However, if I find out about my Omnipotence only when I get upset about politics and wish something (e.g., a country) or someone (e.g., Trump) into oblivion, then my reaction would be anything from "Oops, let's undo that." to "Oh well."
Unless I wake up with the comprehensive understanding of my power, my first day--and some time after that--would be dedicated to assessing my power; its potency, limitations, and any potential requirements.
If I already know everything there is to know about my power, I would safeguard myself (i.e., remove all known and unknown ailments and setup protection so that no one and nothing can do me harm) and then I would start working on plans. Anything from what I can do for myself to what I can do for others (individually or on a grander scale) without revealing myself or destroying (literally or metaphorically) whom I wish to help or what I wish to improve.
After all, simply wishing that there is no more adversity in life may sound wonderful to some, until they realise that facing adversity is crucial component in individual's growth. Even more specific "remove all disease" may actually turn out to be problematic, because there have been many who only achieved what they did because they fought, accepted, or even survived a disease. And there are many other controversial concerns out there.
First and foremost, I would make sure that my secret cannot be spread by anyone other than myself, as well as that my secret cannot be learnt unintentionally (= already a contingency from #2).
As for potentially revealing my secret; if there is ever a person with whom I wish to share my experiences, I would have to reveal at least some part of my secret to include them in my experiences. In other words, even if I don't reveal my secret in its entirety, they might notice something is different when we go explore another universe. And I would probably remove the knowledge if this individual and I ever (permanently) go our separate ways.
No matter what I could say, basically anything is likely going to yield some degree of doubt, confusion, possibly outrage, and--at the very least--questions and long discussions. To avoid these, I would instead "upload" the necessary information to the person's brain. I would not upload everything, merely what's necessary to eliminate the part where I need to prove myself and all the annoying "why" and "how" questions.
I cannot quite decide whether I would care to help humanity or abandon it for another civilisation (alien or created). Either way, I would try to take care of everything big at once and let it run by itself as much as possible from there. This should allow me to focus on and hopefully enjoy the "little things".
That said, I would probably first look into and experience civilisations that already exist (past, present, and future) before I would attempt to create a new one.