The title says it all. When I post questions from my phone I don't get the option to add a picture. I think.
You'll have to use the appropriate markup, or wait until the feature is implemented. The mobile app currently does not support adding photos, at least not that I'm aware of.
The markup is:
: link to image
This functionality has been added to the Android app. When editing a post, you'll notice a camera button below the edit field.
Click the button, and a dialog will appear asking where you'd like to get the photo from.
If you choose
From Device, you'll be able to select an image that is stored on your phone. If you select
From URL, you'll have to enter the URL and press
If using a web browser, follow the instructions in this answer