How can one successfully overcome ageism for experienced workers for those 40-70 years old in the workplace?
Avoid complaining about technology or saying things that make it sound like you are incapable of tech. Look for YouTube videos, or try online courses from edX, Coursera, Udacity, Lynda, and so on to learn the basics of Windows (or OSX), Word, Excel, and PowerPoint, fluent in the use of email and online calendars, and be reasonably familiar with social media, like Facebook and Twitter.
Respect your supervisor even if they are younger than you. They are the boss, not you. If you cannot respect your supervisor as a person, respect the office and the chain of command.