What version of Premiere Elements and what computer operating system is involved?
For now, I will assume Premiere Elements 11, 12/12.1, or 13/13.1 on Windows 7, 8, or 8.1 64 bit.
You can achieve slow motion and fast motion effects in Premiere Elements in 3 ways
1. Interpret Footage dialog. Frame Rate Section and adjust frame rate.
(Right click imported video in Project Assets, select Interpret Footage from menu that appears)
2. Time Stretch
(Right click Timeline video, select Time Stretch, and adjust the Speed %.
3. Time Remapping. (demo was done with version 11
(Tools Menu/Time Remapping for selected Timeline video)
I would suggest that you try each and determine which gives you the wanted slow motion effect with smoothness.
I would start with Time Remapping.
There are advised Speed% changes for Time Stretch for smoothest slow motion...50%, 33.33%, 25%, 20%, 16.67%...that can be found mentioned online.
And, there is this old tutorial on Ramp Slow Motion with Premiere Elements 7. The principles are interesting and are updated and developed in the Time Remapping concept.
As your schedule permits, please let us know of your progress.