How to Edit Signs
First, choose the sign (or signs) that you'd like to Edit.
Note that you can select multiple signs by holding the shift key and clicking on the signs you'd like to select (either on the map, or in the sign list), or by holding the shift key and dragging a box around the signs you'd like to select.
Note that some PC environments don't recognize the Shift-Click for dragging the box... if this happens, try the alternatives of Alt+Shift-Click, or Ctrl+Alt+Shift-Click
Once you've selected the sign, you'll see multiple fields that you can adjust as you see fit.
Note that the fields visible here will depend on the type of the sign (or signs) selected.
If you've selected 2 signs of different types, you'll only be able to modify the fields that are common to both sign types.
You can find more info on fields in sign types here: Manage Fields
When you're happy with the changes you've made, be sure to click the Save button to save your changes.
Once you've made changes and saved them, you'll also see those changes in the Audit Trail at the bottom. To see the difference in the changes you just made, you can click [show diff]