To navigate from ViewModel to ViewModel you can use the following code:
var _pageNavigationService = new PageNavigationService(viewLocator, jsonSerializer);
_pageNavigationService
.For<MainPageViewModel>()
.Navigate();
_pageNavigationService
.For<MainPageViewModel>()
.WithParam(x => x.ParameterName, parameterValue)
.Navigate(shouldClearBackstack);
_pageNavigationService
.For<MainPageViewModel>()
.WithParam(x => x.Name, "Sherlock Holmes")
.WithParam(x => x.Age, 25)
.WithParam(x => x.Gender, null)
.Navigate(shouldClearBackstack);