Instructions
Download a free copy of Pete's GPU plug-in --- the file will be zipped. Open the folder that contains your ePSXe files, and then open the "Plugins" folder inside of it. Drag and drop Pete's GPU plug-in into the folder.
Right-click on the zipped plug-in, and then click on the "Extract All" option in the context menu that pops up.
Open the main ePSXe folder, and then launch ePSXe. Select the "Video" option from the program's "Config" heading. Click on the "Select/Config Main Video Plugin" menu box, when the Config Video menu appears. Select "Pete's OpenGL2 Driver" from the list of options in the menu box.
Click on the Config Video menu's "Configure" button to open the plugin's configuration options.
Click on the configuration menu's "Window mode" bubble. You can use the default resolution, 640 x 480, in the "Window Size" fields, or type in a custom resolution for ePXSe's video output.
Click on the configuration menu's "Stretching Mode" menu box, and then select its "Scale to window size, keep aspect ratio" option.
Click on the configuration menu's "OK" button to apply your settings and return to the Config Video menu. Click "OK" in the Config Video menu to return to ePSXe's main menu.