Hi there and welcome.
This is a really good question, or rather collection of questions about one of the most basic topics, getting started. There is no definitive, one size fits all answer here but I'll do my best and give you my take.
I'm going to assume you are talking about meeting a submissive and/or kinky woman in real life since online it's really just a matter of looking at their profile! In real life (or face to face since online is still real) women do not have a sexuality profile tattooed on their forehead so as you alluded to it's not immediately obvious if someone you've met is kinky or not. The least effective option is just hoping that women you meet randomly under normal circumstances will have some level of kinky interest. It's most certainly not a conversation opening topic so you could be quite a way into a relationship before being able to broach the topic, luckily there is a much better way.
Just imagine for a moment you wanted to find a woman who was instead interested in cars. The obvious thing to do is join car clubs, attend auto meets and shows or motorsport events. This way you are starting out in a group where interest in cars is already established. Being part of an interest community means you avoid the guesswork.
In the kink world there are kink and bdsm communities, joining these will ensure you start with the right people and eliminate a lot of the guesswork. The easiest and most friendly way to get started is seeking out the social meetings for these groups in the form of local munches. A munch is a straightforward gathering at a bar or restaurant venue where kinky folk gather to just eat, drink and chat about their interest. This is not a place to pick up a submissive woman but you can get to know others in the area, find out what events are held and generally get a feel for the local kink community.
Now the second part of this will come into play, there is a LOT of different kinks, not everyone who is kinky is into all kinks and you may not be either. So even when you are among the kinky there will be some hurdles to jump. So the best thing is to learn as much as you can, read a lot, ask questions and take your time.
Kinky people come from all walks of life with every type of background and it's a lot more common than many people think. Don't worry about women being "saints", they can be every bit as perverted and depraved as some men. You have stated specifically you want to find a submissive woman and the biggest thing to understand here is that you need to build up confidence. Being knowledgeable and confident shows through in body language and how you interact, and this is key. Secondly you must be respectful, so don't think you just need to learn some forceful phrases and you will be able to command respect. It doesn't work that way.
Respect earns respect, demonstrating your character, your knowledge and skills is naturally attractive to submissives. They want someone who can guide them, mold them, control them and dominate them and for this to happen you must earn their respect. Be patient, learn as much as you can and get involved in your community.
Good luck.