Are you asking how to create them or how to manage them?
For account creation, what everyone said above will work.
For account management, you will need a third party tool that support multi-accounts management and have the tools that will help you achieve what you want.
For example, if you are going to be joining / posting to groups, then the tool needs to have a tool to find groups and join them and then a tool to post to these groups on your behalf.