You need to roll up your sleeves and muck in, rather than just telling us what to do! 'Muck in' = colloquial. To help others to do something.

It means to actually do the work rather than just talk about it. For example, in a business, you might say a manager "rolled up his sleeves" to mean that instead of asking the employees to do it alone, he also helped on a project.

I agree with Nicholas’s answer. Relatedly, it can also mean “a willingness to work hard”.