You can see a video that walks you through baiting and setting the Victor Rat Trap M326 Pro here.
No, the Protecta Sidekick was designed to hold the Trapper T-Rex Rat Snap Trap.
While the Victor Rat Trap M326 Pro is a larger trap it would not be ideal for squirrels. It might be possible to catch small ones in it, but not larger ones.
For rats inside, it is best to use snap traps, such as the Victor Rat Trap M326 Pro, and glueboards so you can control where they are going to die. You should also seal up all cracks and crevices where rats may be able to enter the structure. Tamper-resistant bait stations with a rodenticide outside would also help if they are coming and going. Please take a moment to review our How to Get Rid of Rats Guide as well as our Rat Prevention Guide for more information.