Register your ficticious name or change your address if already registered with SunBiz https://dos.myflorida.com/sunbiz/
Once registered print your registration and make an appointment with Orlando Tax Office to file for your City tax receipt. You can also apply online or obtain the application and fill it out before going to the office. https://www.orlando.gov/Building-Development/Permits-Inspections/Other/Get-a-Business-Tax-Receipt . If you are a home business, you will want to call and see if there are any special zoning questions or applications you need to submit. You may do better to have a commercial address since this makes for a simpler permitting process.
After you are done at the city you can proceed with Orange County for your county tax receipt https://www.octaxcol.com/obtain-new-business-tax-receipt/ . You can also find the application online and fill it out to save time. You may also apply online.
Doing the entire process online will probably take one to two weeks. You can usually complete the process in one day by going in person.
You must complete this process in the order presented. Orange County will not issue a tax receipt without first seeing the city and state approvals.