First, open the image you want to work with. Keep in mind, when converting a color image to IR, you get better results if you use an image that has lots of greenery in it. Once you get the image open, click on the image icon at the top of the page and 
duplicate the image. Close the original, and just work with the duplicate. Once you do this, click on the layer icon and, in the drop down, go to New Adjustment Layer then over to channel mixer. Once you click here, another box will pop up; click ok here. Next, the channel mixer box will pop up. Be sure to check the Monochrome box in the lower left hand corner; when you do this, the image turns grayscale. You use the adjustments under red, green and blue to make the image b/w. If you're doing a landscape, the green needs to be maxed out at 200; for portraits, the red needs to be at 200. Play with the red and blue (or green and blue) until you have the effect you want. The constant slider near the bottom of the box changes brightness.
Once this is done, click on the layer icon again, and in the drop down, click on flatten image. From here, click on the filter icon, go down to blur and click on gaussian blur. Blur the image using the radius slider; you can watch the change as you do the adjusting. For images that are 25MB, the slider should be between 5-20 pixels. For a 5MB image, it should be between 2-10 pixels.
Next, click on the edit icon and in the drop down, go to fade gaussian blur. Once the box opens up, change the mode to overlay or screen. Just play with different modes to get the effect you want. Drag the opacity slider to the left to reduce the effect of the blur. Where it should be set varies with each image.
You are done, and ready to save your new image to wherever you choose to save it.
