You can also change the length and time from Object Standard Properties.
Select the object and click Insert > Object Properties > Standard Properties. You can change the name of the object from here as well.

You can change the properties by time or by frame. You can enter the starting time and ending time you want the object to be displayed.
By Frame option will give you the similar ways but frame number instead of time. You can also click the Set Frame button to easily find the frame or time. Once you set the numbers in this window, click Set button to save. These values will be applied to Object Standard Properties window.

In order to verify if the object is properly added, you can simply play the movie. You can either click the Play button from slide window or select Play button from the Play menu.
Please note that you can’t edit while playing the video.