Sheldon Brown has the answers you seek: https://www.sheldonbrown.com/fixedgear.html

https://www.sheldonbrown.com/singlespeed.html

I also recommend keeping the brakes on your bike. You can still skid to your heart's content but in an emergency, they can be life savers.

I've done several conversions and they turned out very well but cost more than one might be willing to pay for a new SS/FG bike. The links posted above can help you stay on budget.

You can use that Bianchi for your conversion. Is the rear hub a freewheel or a freehub? https://www.sheldonbrown.com/free-k7.html
If it's a freewheel(quite possible), you can use the wheel as is with a cog of your choice. If it's a freehub, I'd just buy a SS/FG wheelset with flip-flop hub. Take the wheelset to a bike mechanic who can make sure the spokes are evenly tensioned and the rims are true. Sun or Velocity rims, Formula hubs, Sapim or DT Swiss spokes provide great value for the money.

Whatever you do, don't grind off any parts of that Bianchi.