You would get a hanging type holder for the sock and your input water would go through it as it enters the sump.
So to the far left of the sump. I have several setup this way. Filter socks are a blessing, some people hate em, BUT use one for a week and see what it catches and you will be sold on the idea. lol Bulk reef supply has cheap socks, i would get like 4 so you can rotate them in and out. Depending on whats going on in your tank you will have to change it once a week or more frequently.