Research the variety of A-framed porch swing plans available. Determine which set and what size porch swing you'd like to build.
Cut four of the 4x4's to length and add the A-frame brackets. Join the ends to create two basic "V" shapes.
Saw the 2x4's to size and secure them across the middle of your "V," creating the "A" shaped forms that will hold your porch swing.
Secure the A-frames to the last 4x4. This is the bar that your swing will hang from.
Add the porch swing bolts that came with your A-frame brackets. Measure your swing and place those bolts so the swing will be centered within the A-frame you've built.
Secure the porch swing chains to the bolts in order to to hang the swing from the A-frame.
Place your A-frame porch swing in the location of your choice. If placing your A-frame porch swing directly onto the lawn, you'll want to stain or paint the A-frame porch swing to protect it from deterioration. Make sure the swing is level for safety.