To place components in your schematic, you may either double-click the left mouse button in the Graphic Editor window, or use the corresponding menu command:
Symbol -> Enter Symbol
When the Enter Symbol command is executed, a window containing the available libraries and symbols will show up. If you know the name of the symbol you may type the name in the Symbol Name box at the top of the window. Otherwise, you will need to browse through the various libraries until you find the symbol you want. To view the components available within a library, double click the left mouse button on the appropriate directory in the Symbol box. The symbols contained in that directory will show up in the Symbol Files box. Select the desired component by double clicking the left mouse button on its name in the Symbol Files box. The selected symbol will appear in the Graphic Editor window.