To add or modify pick list values, do the following:

1. Log in to CRM with Administrator privileges.
2. Click Setup > Customization > Fields.
3. Select the Module from the drop-down list.
4. In the [Module] List page, click the Edit link corresponding to the pick list that you want to modify.(For example, Lead Source field)
5. In the Edit Pick List page, you can do the following:
• Click Delete icon to delete the pick list value.
• Click Add New Values for additional pick list values.
• Modify the values, if required.
6. Select the Use first value as default value check box, if required.
7. Click Sort values alphabetically, not in the order entered, if  required.
8. Click Save.

• Delete the values - When you delete a picklist value, the records that have the particular value will NOT be deleted.
• Edit the values - When you edit the value(s), it will not be automatically updated in the records where it is used. You need to individually select the records and update the picklist field.
• Replace the values - When you replace the value(s), it will be automatically updated in the records where it is used. You need not individually select the records and update the picklist field.