How to generate the copyright (c) symbol and other things like that

Just answered your question about slide numbers. I pointed to the X button in the Character part of the Properties panel, you'll find symbols to the left of the X button:

The last one is to insert a hyperlink (which can do much more than just create a link, can trigger advanced actions).

For other symbols than the limited ones listed there, I often switch to Wingdings or Webdings font if the symbol is not available in the font I'm using.