At the top panel, choose the type of output format you would like to convert to (Video / Audio / Device / Website). Then, choose the output format and profile at the top panels.
Add the SWF files you would like to convert to WEBM by clicking the "Add Files" button at the right pane. Automatic capture is supported in non interactive animations and some screencast recordings (for example, in Jing screencast recordings).
Once you click the "Convert!" button at the bottom-right corner, the software will start to capture the SWF file. Once capturing completes, it will convert this recording to WEBM.