I'm confused... you say you downloaded Premiere Elements 8... then you say you HAVE Elements 8... just what do you have... the FULL name?
I have Adobe Photoshop Elements 8 and I am quite happy with the way it does slideshows.
I downloaded Adobe Premiere Elements 8, the free trial, in hopes that it would do the same as Photoshop elements 8 with added features that it advertises namely "stunning video slide shows with Hollywood style". It doesn't. It is slow. I can import media but to then drag it into the slideshow it has to be done one at a time. It runs so slow. The effects and transitions are not impressive and from time to time the software crashes.
My source files are simply pictures from my hard drive which I import. My goal is to create slideshows for personal use with stunning transitions and effects. Adobe Photoshop Elements 8 does good slideshows for me and I have no problems. I guess I expected too much from Premiere Elements 8. I have a friend who when he starts out a slideshow a drop of water hits the water surface and opens up to an image. I have no idea what he uses but I expected premiere elements 8 to be able to do this.
First, I highly recommend that you resize your photos to no larger than 1000x750 pixels before you bring them into a Premiere Elements project. You'll get the best quality doing this as well as the best performance.
That said, you still haven't said how you're creating a slideshow in Premiere Elements -- but as I said there are two automatic slideshow creators built into Premiere Elements in addition to the workflow that interfaces with the Organizer. So, depending on your goals, as I said, there are a number of ways -- both automatic and manual -- for achieving your goals.
I don't know, for instance, if you plan to create a slideshow just to watch on your computer, to display on a web site or to burn to a DVD, but the three Elements programs (Photoshop, Premiere and the Organizer) are designed to work as a bundle to help you accomplish whatever it is you're trying to do as efficiently as possible.
What size are those images which you are importing? PRE is not optimized to work with very High-def images hence that might lead to a problem.
Maybe I am missing something here, but in PrE, you can Import as many still images as you need. From the Project Panel (where these are shown, after Import), you can click-drag, or Shift-click-drag (for more than one) them to the Timeline, or to the Sceneline. You can order them, as is needed. There is no need to do it one image at a time.
Now, as has been said, getting your still images resized before Import is a very important step. This ARTICLE will give you some tips on doing it in PS/PSE in an automated fashion. This will improve performance greatly and will also result in better quality - this is one time that "bigger" is not "better."