Start by choosing the location and marking the top and bottom positions.
Drop a plumb line to make sure top and bottom positions are vertical.
If you are replacing a load-bearing post, brace the roof with a jack post before you remove the old post.
Measure the height of the space between the decking and upper beam. The height of this space is the height of the post.
Cut the pressure-treated post to fit.
To allow for expansion, the post sleeve should be slightly shorter than the pressure-treated post.
Cut the post sleeve and slide it over the PT post. Set the post sleeve skirt in place at the bottom of the post.
Use a level to plumb the post.
Tape the skirt out of the way before pre-drilling the post bottom.
To attach the bottom of the post, pre-drill with a countersink bit on all four sides at a toe nailed angle making sure you drill through the sleeve and post and into the deck.
Screw the post into the deck and lower the skirt.
Pre-drill the top of the post and attach to the upper beam.
Make sure the weight of the roof is on the pressure-treated post, not on the post sleeve.
Fill screw holes with matching wood putty.