Windows Store App; xml, storage, and files

I am having a real hard time getting my simple XML files to work in WSA.

Apparently I cannot use System.IO due to security, and I am also having issues with XmlWriter. I would really appreciate some help, Ive read a thousand articles on the topic but the tactics I've seen seem to be outdated.

                     XmlWriterSettings XWsettings = new XmlWriterSettings();
                     XWsettings.Indent = true;
                     
                     // INV ITEM
                     System.Xml.Serialization.XmlSerializer inv_writer = new System.Xml.Serialization.XmlSerializer(typeof(List<inv_item>));
                     
                     // convert string to stream
                     //byte[] byteArray = Encoding.UTF8.GetBytes(inv_list);
                     //byte[] byteArray = Encoding.ASCII.GetBytes(contents);
                     //MemoryStream stream = new MemoryStream(byteArray);
                     
                     // INEVENTORY 
                     using(XmlWriter Xwriter = XmlWriter.Create("inventory.xml", XWsettings))
                     {
                         inv_writer.Serialize(Xwriter, inv_list); // Can circumvent needed FileStream object
                     }
                     
                     // EQUIPMENT
                     System.Xml.Serialization.XmlSerializer eq_writer = new System.Xml.Serialization.XmlSerializer(typeof(List<equipable_item>));
                     using(XmlWriter Xwriter = XmlWriter.Create("equipment.xml", XWsettings))
                     {
                         eq_writer.Serialize(Xwriter, eq_list); // Can circumvent needed FileStream object
                     }
                     
                     // GEMS
                     System.Xml.Serialization.XmlSerializer gem_writer = new System.Xml.Serialization.XmlSerializer(typeof(List<skill_gem>));
                     using(XmlWriter Xwriter = XmlWriter.Create("skillgems.xml", XWsettings))
                     {
                         gem_writer.Serialize(Xwriter, gem_list); // Can circumvent needed FileStream object
                     }