For winter it’s always nice to re-caulk the windows. I am not an expert so I am not sure how often this should be done. All I know is our windows needed it .. per our inspection report .. and because some of them were peeling. Also upon removing old window treatment hardware, it peeled some of the old caulking off.
First, load your caulking gun with the proper caulk. I make a 45-degree angled cut about 3-4 mm from the tip of the bottle.
I chose a water based caulk so it comes off easily from your hands. This was also an indoor/outdoor caulk so in case we need to do some outdoor windows we have 3 extra tubes .. or we can return them. They were only $1.20 I think so it’s not a huge loss.
Next, caulk the windows with a plentiful amount. I try to go from corner to corner individually.
Notice I am using both hands. It helps for support. Also it takes a lot of strength to squeeze as hard as you need to. Sometimes you need to release and start squeezing again. DO NOT lift the tip off the window: simply stop, release, start squeezing again and continue along the window line.
Once in a while you’ll get some air bubbles but don’t worry about those. In the next step you will get rid of those.
Finally, set the caulking gun aside (being sure to release the pressure to the tube). Then you want to take your finger and lightly smooth out the caulk lines. 
They make tools for this step but your finger works just as well and if you get the water based caulk. It washes off so easy!
So that is how I caulked all 20 of our windows in our new home before my wonderful husband put up new blinds in all of them. Took us a full week working on it off-and-on but we finally finished it all today!!! Just in time to relax for the Superbowl!