In the side bar at the left, select Custom fields. A list of all configured custom fields appears.
Click Add Custom Field in the top right corner. The dialog "Select a Field Type" appears.
Select the appropriate field type and then click Next.
Enter a field name; then click Create.
Repeat the steps 2 - 5 to create all custom fields you need.
To re-index your field configuration, click perform a re-index in the pop-up dialog in the top right corner. Select System in the JIRA Administration menu and then Indexing in the "ADVANCED" section of the side bar at the left.
Select Re-Index in the "Re-Indexing" dialog. Wait until the re-index is completed.