There are two ways. The quick way -- alt-right click on the blue bar above the timeline. The slow way (and the best if you are planning a long animation) is to click on "File" then "Project Settings" -- up comes a panel where you can type in the new end frame. Thank you :) Maybe...

Hi, I'm very new to Anime Studio. And i wonder how i can make my animations longer than 72 frames (change the length of the animation).

Thanks in advance