How do you find a job when you are over fifty and been a stay at home mom most of the last twenty years?

I have a master's degree in international management and a CFA plus six years professional experience (mainly from twenty years ago) want to work in investment management

I have been in managment for 25 years and have never heard of International Management? what is that

I would start at your local temporary placement agency. Some of them can place management level people and it's a great way to get your feet in the door.

Put yourself out there... Check out popular job sites and send your resume to as many as possible. You can probably even exaggerate a bit and say that you did some "consulting" to build some credibility in the experience department.

I'm sure that a lot has changed. You're probably going to have to begin somewhere near the bottom (entry-level).
You will move up quickly I'm sure. Work on your resume. What skills and experience do you have for the work you want to do? You should start networking if you haven't already. Join the women's business group. Rotary is a great organization that brings business people together. Send your resume off to banks and investment groups. Check the job sites and your local newspaper. Go to a local college to see what jobs are available at their career center.