Tab Bar Customisation (tab bar item positioning) with Tabview in SwiftUI

Question

I am trying to figure out how to use the functions from xcode with very limited information from the Apple documentation. How to use certain functions or variables or where to find examples and detailed explanations? The particular case that I am working on now is to offset the tab bar item images on the tab bar. I came across "itemPositioning", "stackedItemPositioning" but I have no clues about how to use them. Should I put it inside the initialiser function? And how to use it?

Also, a quick question. Is there any book or video covering like somethings that teach me how to explore unknown things on SwiftUI independently?

truct MainContentView: View {
    @State private var navSelection = 0
   
    init(){
        UITabBar.appearance().backgroundColor = UIColor.clear
        
        
        //stackedItemPositioning = UIOffset(horizontal: 0, vertical: -10)
    }
    
  
    var body: some View {
        
            VStack(alignment: .center){

                NavigationView{
                    TabView(selection: self.$navSelection){
                        Text("hey")
                            .tabItem{
                                
                                Image(systemName: "heart.fill")
                                    .offset(y:-15)
                            }
                            .tag(0)
                            
                        
                        Text("hey")
                            .tabItem{
                                Image(systemName: "magnifyingglass")
                            }
                            .tag(1)
                        
                        Text("hey")
                            .tabItem{
                                Image(systemName: "capsule.portrait.fill")
                            }
                            .tag(2)
                        
                       Text("hey")
                            .tabItem{
                                Image(systemName: "wand.and.stars")
                            }
                            .tag(3)
                   
                    }
                   
                }
                
            }
        
    }
}