Use Tools > Options > Keyboard
The available functions (and scripts) that can be assigned shortcuts are listed, allowing you to seen and edit the shortcuts. For example, to assign the shortcut CTRL+SHIFT+1 to the Block Comment Toggle script, select it in the list, click in the Assign Shortcuts edit box, and hit the desired keyboard shortcut keys (causing “Ctrl + Shift + 1” in this case to appear automatically), then click Add.
Note that a function can have multiple shortcuts assigned, but if you try to assign a shortcut that has already been assigned, it will just display a message indicating the conflict. For example, if we try to assign Ctrl+Shft+1 to Doc Search:
