MAKE SURE CUSTOM TEXTURES ARE ON by opening dolphin, clicking "Graphics", going to the "Advanced" tab, and checking "Load Custom Textures"

1) Rename your desired trail to this:
Pit: tex1_64x64_03301a747dd1af73_4.png
Dark Pit: tex1_64x64_3abf53b37af49809_4.png

2) Open the P+ Folder and place this image anywhere within User\Load\Textures\RSBE01

3) You're done! :)

