You've successfully saved a symbol into your symbol library and now want to use it but cannot see it in the Add Component dialog. The reason is that you also need to create a Component for the symbol in order to add it to the design.  Typically a component will use two symbols (one schematic and one PCB) though it's possible to just have one of these or several of each.

Once you've created the Component containing your symbol, providing it is correct, you can use the Add Component dialog to locate it and add to the design.

Symbols only contain the graphical elements of a component.  The extra links and non-graphical information are only stored in the component, so both are needed in a design, symbols alone would not work.