1. Go to the fields area of the object you want to create a picklist field for.
2. In the Custom Fields related list, click Edit.
3. Click Promote to Global Value Set.
4. Enter a label for the global value set.
5. Accept the Field Name or edit it.
6. Optionally, enter a description to identify it when using the values for other custom picklists.
7. Click Promote to Global Value Set, again.