Once you complete an internationally recognized PDC there are quite a few permaculture designer directories you could create a profile in; that would help people who know about the directories find you. I'm not sure how effective the directories are, but they are an option for being discovered. permaculture education directory
| Permaculture Global directory
Most people that consult internationally seem to have 15+ years of experience across multiple biomes and people generally go to them. With your experience, I would try and focus on your local community and surrounding biomes at first and contact individuals or organizations that might be interested. (cold call / email)
An important part of being doing anything professionally is building your client base and gaining brand recognition. Most people don't know the word permaculture so creating a website such as <your location> forest gardens may make it more accessible. You will need to be sure that potential clients have a good way to book a consultation whether that is in person or via something like zoom or skype. See my website as an example: permapromoters.com
Some ways of gaining clients organically could be creating your own PDC, starting a YouTube channel, blog, or podcast. If you can show people that you know what you are talking about they will come to you. You could also pay for advertising, post on craigslist, hand out business cards at your local farmers market/club/meeting/whatever any way you can pay to get your service in front of potential clients. Over time you will get more organic traffic & clients as people hear about you from others. You could also try creating a profile on freelance services such as fiverr
although I doubt those services are as effective as having your own channels even though there is low competition there.
Alternatively, you can try and get on board with an existing landscaping company as a designer and they could help with implementing designs you create. You should also familiarise yourself with all your local nurseries, farms, & other designers, and what they offer.
Personally, I like to diversify what I offer quite a bit. Are you just doing online consulting or are you willing to drive out to a site, are you going to do soil testing, lidar scanning, surveying? Are you going to create hand-drawn or digital designs, are you going to print them out? Are you going to order plants for customers or just create lists of where they can get them?
Really it is all about getting your name out there but I would defiantly chat with established designers/consultants, look at their websites and get a feel for what others in the industry are doing. And if there is something you don't have the equipment or ability to do (i.e. digital art) then outsource it to another designer or if you need to collaborate with another designer that is more familiar with an exotic biome. Many consultants collab to provide a better service.
As for getting your first client, you will need a good portfolio, perhaps start with friends and family or offer 50% off for your first customer. I don't know if anyone gets by from just offering advice, you need some kind of reference point, review, or image that shows what you teach works at that is something that takes time. (because plants grow) lol
There is a lot more to it, but I hope something in what I wrote here helps you get started.