There is a free adjuster's manual available on line. If you go to my resources page and scroll down to the link about FW you will see it.
First remove the needle plate. Betsy is demonstrating this. I like to use the Brownell bit set. She, however, is a fan of the long shaft screw driver.
Now the proverbial finger of the bobbin case is released from the position bracket on the needle plate. When you replace the bobbin case base be sure it is positioned correctly with the finger nestled in the position bracket. (This is a 301, it is the exact same concept though the parts are not necessarily interchangeable)
Loosen the gib screw that holds the gib in place and rotate the gib outward.