I don't know about finance or accounting, but in engineering you generally have three options.
1. Apply for a scholarship from an external organization. Which organizations are available to you will depend on many factors, e.g. your country of citizenship. U.S. citizens can apply for the Fulbright scholarship. German citizens can apply for the DAAD scholarship. You'll have to research which scholarships may be available to you. If you get such a scholarship then applying directly to a professor of your choice will be easy because you won't cost them much.
2. Apply to posted PhD positions. Research institutes and individual professors at universities often publish available PhD positions on their websites. You'll have to check your research institutions of choice periodically to find those positions.
3. Contact professors of your choice directly and ask if they have funding available. This method is the most difficult because professors get hundreds of emails per year. If you choose this approach you must
a) thoroughly research their topic and current projects so that you can explain why you have the background, skills and interest in helping them investigate their project.
McDVOICE
b) apply in flawless English. As a PhD student you are expected to learn scientific writing. This style of writing is challenging even for native speakers. Professors will only invest their time into students that they believe can achieve a level of English where they are able to independently produce scientific manuscripts.