Find two pictures that you want to face swap and copy and paste them into photoshop.

Step 1: Put Your Photos Side by Side

Find two pictures that you want to face swap and place them right next to each other.

Step 2: Select the Face That You Want in Your Photo

Select the lasso tool on the toolbar and carefully trace around the eyebrows nose and mouth.

Step 3: Copy and Paste

Press ctrl+c to copy the selection and ctrl+v to paste the copied face.

Step 4: Move the Face Over

Select the layer that contains the face and move it over to the body you want the original shot you want to replace.

Step 5: Rescale the Face

Change the face layer opacity to 70% to see beneath the layer and scale it so the eyes, nose, and mouth align. (You won't be needing the image you got the face from.) After rescaling and adjusting change the opacity back to 100%

Step 6: Duplicate the Original Photo

Duplicate your original photo by pressing ctrl+J or right click the layer and duplicate layer. Rename it "copy"

to avoid confusion. Click on the eye to hide that layer

Step 7: Create a Clipping Mask

While pressing Ctrl, click on the thumbnail of the face layer. This will select the shape of the face on all three layers. Then hide the face layer.

Step 8: Create an Overlap of the Face With the Copy

Click Select in the photoshop menu and choose Modify then Contract. Type 10 in the the dialogue box. This with shrink the allow the face to overlap the copy by shrinking the clipping mask by a few pixels.

Step 9: Delete the Face Outline From Copy Layer

While the copy layer is selected, delete the area beneath the face. Deselect.

Step 10: Select the Body and Face Layers

Click Edit in the menu and select Auto-Blend Layer. Choose Panorama and check both the "Seamless Tones and Colors" and "Content Aware Fill Transparent Areas." Click Ok.