How to use SVG Images as Controls and Form "Background" (or customisation)?

I tried several Nuget packages and followed their description of implementation. But since I'm very new to Xamarin and C# I can't get it to work Image may be NSFW.
Clik here to view.
Could someone please precisely describe how to implement a svg image as a fully working control or as Forms customisation? Some links to learn the missing basics would also be very appreciated XD.
Thanks in advance, Jan.