1. Go to Settings -> Advanced Configuration -> Fields
2. Select Module name -> The existing fields in the module are shown
3. Scroll down and select the picklist field you want to change, click on the field name. The field details screen will open
4. Click on ‘Edit Pick List’ . You can add the picklist value in the given text box and click on ‘+’
5. Close the screen and save the field by clicking on the floppy icon