First, watch one or two YouTube clips. Next, mistrust video learning, so browse a few pages of home-improvement books at the library. Confirm most of what you watched online. Draw up a vague shopping list of necessary supplies. Head to the hardware store and spend at least an hour, dizzyingly considering the pros and cons of products for stripping wood finishes, the relative merits of competing stain brands, the incremental arrays of sand-paper grains, just the right brushes for the job, and so forth. Tell a parade of employees who ask if they can help you that you're doing fine. Return home, exhausted and amply equipped.
Lay down newspaper in the work areas because you're marginally responsible. Stir stripping goop a paranoid amount and brush on. Wait. Scrape off the goop along with (most of) the former finish. Discover, through trial and error, the sweet spot that achieves this purpose without gouging the wood. Wait again for surface to dry. Remove lingering bits of tenacious finish with three different flavors of sand paper. Not only does this buff out many gouges, you'll learn it also opens the wood for subsequent stain absorption. Vacuum up sandy residue. Brush on wood conditioner, which will promote even staining. Wait while conditioner dries. Brush on stain. Wait for more drying time before applying second coat.
Now the big wait: over night for stain to dry thoroughly before applying finish.
The next day at dawn, three thin layers of finish go on, requiring at least two hours of drying between each. (Incidentally, this makes a fine excuse to read, which will help you put a dent in any magazine piles lying around.)
And the payoff, from before:
That unsightly hole in the screen will be gone soon when the window is replaced to do its refurbished sill justice. That, by the way, will be a job for professionals.