Participation in the political process outside of work and during non-work time is admirable. You can make lawful contributions to political activities; however, Walmart will not reimburse you for those activities unless required by law. You cannot use your job title or company affiliation in connection with political activities unless that information is required by law or allowed by company policy.

Political contributions, direct or indirect, of company funds or use of company property, services, or other assets for political purposes may not be made without the prior approval of the Government Relations Department.

I would like to sit on the Education Board for my city. Am I allowed to do this as a manager at Walmart?
Yes. Make sure your position with Walmart, and any influence related to it, is kept separate from your newly appointed position on the Education Board.