tl;dr
Sell the Century mount and get one that is for the Vortex Spitfire
I don't have any of those rifles, mounts or optics but after doing some research it looks like you bought the Century mount that is intended to be used with a standard screw pattern red dot like an Aimpoint or Primary Arms MRD, but you bought a picatinny Vortex Spitfire instead
Nothing wrong with liking the Spitfire but you will need to change the side mount to accommodate it. There may be micro red dot screw pattern to picatinny adapters out there but I don't recall seeing them. Could be tricky to find it if it exists, IMO it's better to buy the right side mount rather than hunt for an additional piece that is a compromise solution.
What you need is a side mount that already has a picatinny rail on top - and there are zillions of choices, so no worries there.
If it was me I would go with the RS Regulate, a Russian NPZ mount or something similar. Those are the best options on the market bar none though they are not the cheapest...I don't know what you intend to do with this rifle though or how important quality is to you.
Sounds like it's just a range toy so in that vein any decent mount will work, just find something that already has the picatinny rail on top.
http://russianoptics.net/mounts.html
Welcome to the forum, and to the Dark Side
Z