Open the "Audience" → "List of segments" and click "Create segment".
Click "Add segments": the list contains the segments and data sources you added earlier. Select the desired pixel from the list.
If you want to include people who have interacted with the pixel in your audience, set the target to Marked; if not, select "Not marked". Specify the time for which the data is taken into account and click "Add segment".
You can create new segments based on existing segments.
After that, configure the created segment