public class ModuleAModule : IModule
{
    private readonly IRegionManager _regionManager;

    public ModuleAModule(IRegionManager regionManager)
    {
        _regionManager = regionManager;
    }

    public void OnInitialized(IContainerProvider containerProvider)
    {
        _regionManager.RegisterViewWithRegion("ContentRegion", typeof(ViewA));
    }

    public void RegisterTypes(IContainerRegistry containerRegistry)
    {
            
    }
}

Iregion region = _regionManager.Regions[“RegionName“];
region.Add(viewInstance);
region.Remove(viewInstance);
region.Activate(viewInstance);
region.Deactivate(viewInstance);