In FireTXT text editor, you can copy or paste text as usual but while running any other console application in FireCMD and in FireCMD's execution mode, you can't select text directly. To select text you should first enable "Selection mode". Selection mode can be enabled by selecting the last tool that appears in the toolbar or by checking Selection mode from Tools menu. You can also use keyboard shortcut Ctrl+M to enable/disable selection mode.
To copy text in console emulator environment and in FireCMD's execution mode, you can use context menu (The menu which appears on right-click) or select the copy action from toolbar or from Edit menu. Shortcut Ctrl+C won't work in FireCMD's execution mode but can be used in command mode. Same thing applies for pasting text. Shortcut Ctrl+V does not work and to you can paste text using any of the three methods described above for copying.
Note: It is advisable to disable selection mode if there is currently no need of text selection. Disabling selection mode provides a better emulation of console.