Hello, and welcome onboard 
Depending of the version you use (Chrysalis 0.8.x introduced a new key picker), and the keyboard layout of your operating system (QWERTY, Colmak, Dvorak, …) it may vary.
For instance, to have an @ with an AZERTY
keyboard, I need to press AltGr+Ă (the 0
key on qwerty keyboard), so here I go :
- choose your language to reflect the disposition of your keyboard
- Select the
Pick a key
button
- pick the key where your symbol reside on your standard keyboard
- assign the modifiers needed (eg. Shift, or AltGr) if any
The symbol representation may not be accurate (there is a work in progress on this), so you may need to save your configuration and test in a text editor 
If you don’t succeed, tell us which keyboard layout you use and what symbol you search, and we’ll try to figure it out 
Happy hacking !