Without knowing the specific industry you're targeting I can only provide general advice.
However, my background is in the technology sector with primarily specific experience in the Telco & Transport sectors. So if I draw on my own experience I would work through the following steps.
1 - Brainstorm the top 3 topics you feel you are confident to speak about and could mould around a specific engagement.
2 - Identify the regular speaking opportunities locally and regionally that you could attend without too much trouble.
3 - Reach out to your network. Let people know you are looking for this kind of opportunity
4 - Be totally willing to speak for free to build up experience as well as a name for yourself.
Everyone would love to walk straight into a paid speaking gig. The reality is that you have to build up a reputation first and only then will people be willing to pay for your services.
Some events, once convinced of your value add, will be willing to pay for your travel costs but not your time. If you can start by getting those you are doing well. Go to the event. Smash it out of the park. Network like crazy. Build a list of other opportunities to pitch for.
Once you have done a few 'free' engagements you can use those as a springboard in your marketing to help draw in paid work. Obviously having a strong social media presence with videos of you speaking at events and details of where you have spoken in the past and are due to in the future greatly help.
Also look at local business support groups where you can build up a following as a 'go to' guy for your sector.
There are a number of approaches you can take and will vary by your background and target audience.
I hope that gives you a little bit of a pointer in how to get started.
Feel free to schedule a call if you would like to discuss further.
Wishing the best for you