You can copy and paste Games and Positions between chess software using the Copy and Paste submenus of the Edit menu.
To copy a game in the current tab, use the Edit->Copy->Game menu item, the game is then copied to the clipboard. If you are copying from another chess software application please consult the manual/help for that application on how to copy a game in PGN format.
To paste a game from the clipboard, use the Edit->Paste->Game menu item.
For more details please see the Edit menu section.