ok, the fldigi package comes with three executables: fldigi-shell, flarq and fldigi. You can run them by by entering those commands in a terminal.
The documentation for these in the man pages. Eg in the terminal run:
As for your problems with booting the pi, from the information you provided I can't tell what to do to get it working. Couple of questions:
- Exactly what error messages are you seeing?
- Can you get a terminal?
- Are you able to ssh to it?
If you have not customised it much since the installation you can always reinstall on another sdcard.