What computer operating system is your Premiere Elements 12 running on? For now, assumed Windows 7, 8, or 8.1 64 bit.
Typically, if you increase the length of a video clip, you will create slow motion. If you decrease the length of a video clip, you will create fast motion effect.
You can right click the clip on the Timeline, select Time Stretch, and use the Time Stretch dialog's settings to change the video duration.
See the Adobe document/section on Set Duration of Clip
Add On...As an aside, if you have not done so already, please update 12 to 12.1 Update, using an open project's Help Menu/Update.
Great news. Great job.