1. Verify that Lightning Runtime is enabled for flows before building a flow. Find this setting on the Process Automation Settings page in Setup.
2. In Setup, enter Flows in the Quick Find box and click Flows.
3. Click on the New Flow.
4. Drag a Screen element onto the canvas using the flow designer.
5. Leave all other options with their default setting and name the screen.
6. Select the Add a Field tab, and double-click LightningComponent to add a Lightning component field.
7. Click the newly created Lightning component field.
8. Enter a name for the field in Unique Name.
9. Select force Content:file Upload in the Lightning Component picklist.
10. Select the Inputs tab and enter a value for the File Upload Label. This label appears for users in the flow above the image upload component.
11. Select Create New Variable for Related Record ID.
12. Enter Id in Unique Name,.
13. Select Input and Output for Input/Output Type.
14. Click OK.
15. Click Add Row beneath Related Record ID.
16. Select Allow multiple files for Select Attribute.
17. Next to your newly created Allow Multiple Files attribute, in the values picklist, now select GLOBAL CONSTANT | $GlobalConstant.True. This setting gives your users the option to upload multiple images.
18. Click Save.
19. Enter a name for your flow in the window that appears. Remember that the Unique Name that is automatically generated when you name your flow because you need the unique name to connect the flow to the Field Service Lightning mobile app.
20. Select Field Service Mobile Flow for Type.
21. Click on OK to save your flow.