Is it a simple graphic? With only one layer?
If "Yes", then as you're importing the Photoshop Doc (PS) into Premiere, you will get a prompted for something like this "merge the layer", "layer 1", Layer 2' ,etc... Select the layer that contains the graphic only.
If it's more complicated (drop shadows, multiple layers) then make sure the background of your PS file is all white or black. Import it with Merged layers. When you place it on the timeline, do a right-click, select transparency, and then try either black matte or white matte.