To render file follow below steps:
1) Click on File menu, then click on Render
2) Type name with extention (.avi, .mov, .fla) and click on "Choose to" and select the destination, then click on "Ok" button
3) Select target "ffmpeg", set quality "8". Then click on "Render" button.
4) You have to wait, observe, and confirm the message that "File rendered successfully" this message will shown above time line bar where animatoin play menu buttons are placed.
5) Once you got the message, you have to check that destination. You can see render output file.