Resonator Placement?

Here's my situation. I have a 2005 Tundra with a Flowmaster muffler installed (Pictures included). I got an MBRP catback system for Christmas because I love the sound of it. I want to install the resonator to get that sound, but I can't just clamp the whole system in because of the aftermarket muffler that's already installed.
So what do I do? Where do I place the resonator? Can I place just the resonator in between the cats and the muffler? In the reference video, the resonator seems to come after the stock muffler. Is that normal?

I'm just very confused and I feel in over my head since I don't know much about exhaust systems.

Reference video for installation on stock truck:https://www.youtube.com/watch?v=1momgSQ1kMw&t=389s

Catback system I have (the one I want to install):

$395 MBRP S5330AL AL 3" Single Side Exit Resonator Back

https://www.amazon.com/MBRP-S5330AL...7-4691--8-1---&vehicleName=2005+Toyota+Tundra

 

Might wanna take it to an exhaust shop.

Looks like the new exhaust kit is just a muffler and a tail pipe. Probably need to cut the current muffler out and weld in the new one.

 

@dirtydeeds can tell you as he is our exhaust go-to guy. Give him a call. I guarantee that you will learn some things.

 

See attached image. If you're never going to use any of the old again I'd say cut it off at the red line. Hold your new section in place and see where the end (of the inlet side of new) of it goes while the exit is lined up where you want it, then cut where necessary, I'd assume somewhere around the blue line, then just use an exhaust clamp to hold it on or weld if it's an option. Make sure you check tube sizing with calipers or similar to make sure that long straight aftermarket section (that's already on the truck) is the proper diameter to fit the new aftermarket section you want to install.