Go to form builder. Open menu "Actions" (1). Select option "Run" (2) to open proper popup (3).

Popup "Run" allows to pass some data to the form (available from version 5.0):

• the record Id (4)
• the process instance (5)
• the custom parameters (6)

In case you do not need this, just click "Run" button (7) to open the form preview in another browser tab.

Check "Pass Record" checkbox (4) - the record selector will be shown (8). Type ID into field (10) or click settings button (9) to open list of Records names (11, see screenshot below):

Filter (12) if necessary and select Record Name (13). Click "Apply" (14) to pass Record ID (10):

Check "Pass Process Instance" checkbox (15). Type Process ID (17) or click settings button (16) to open list of processes (18).

Filter (19) and select process version (20). Click "Apply" (21) to pass process instance ID. From renderer will get this ID in "workflow" parameter.

Check "Pass Custom Parameters" checkbox (22). Proper sub-form will be shown. Click "Add" button (23) and set parameters. Type name and value of parameters to be passed to the form.

Finally click "Run" button (24) to preview the form.