Hello,
Ok there a few things, I will give a few steps that need to be completed, should be relatively easy to get working,
1. Extract ePSXe to a folder location of your choice on your PC
2. Then you need the PS1 bios file to be placed into bios folder, this can be obtained quite easily with a search online for - SCPH1001 but it is not legal to use anything other than your own bios file from your own PS1
3. Make sure you have extracted the iso of the game you downloaded as it will come in compressed format.
4. Place the extracted contents of your game into the iso's folder
5. Launch the emulator by double clicking the PS1 controller icon
6. The emulator will open, across the top you will see an option named config, click this.
7. at the top you will see option then called wizard guide, click that.
8. follow the prompts at each stage, it ask you to select your bios file, video plugin, sound plug in, cd rom plugin, and finally your controller plugin.
9. All of the plugins are a simple select with mouse click and next until you get to the controller, at that point you must have had controller in from time of launching emulator, you then need to assign the controls & buttons to the controller you are using on your PC, I like the xbox 360 one with usb connection myself.
10. Once done, back on emulator main screen, select file, then run iso which will open a navigation window, navigate to your iso folder where you stored your extracted game.
11. select game and click open.
you should now be in position to play your PS1 game.
hope it works for you, if you encounter and issues graphically or with sound or frame rate, it may be back to your PC's performance and video card etc.
good luck.
What I have owned to date.
Sinclair ZX spectrum, Atari 2600, Commodore 64, Atari ST, Amiga 500, Sega Master system, NES, SNES, Sega Mega drive, Playstation 1, Playstation 2, Gamecube, Playstation 3
What I am emulating,
KEGA, MAME, Nestopia, Mupen ++, PJ64, 1964, NullDC, DEMUL, ePSXe, PCSX2, DeSmuMe.