Step 1, create a fuss over "ukraine" shelling Nuclear power plant
Step 2 Invite in governing body to verify it's about to go boom
Step 3. Make the area part of Russia
Step 4. Make powerplant go boom
Step 5. Blame the west/Ukraine for using Nuclear weapons on Russia
Step 6. Use Nuclear weapons in "self defence"
I don't know why everyone is obsessed with Putin using nukes, even a tactical nuclear weapon wouldn't be of very much use on the battlefield against dispersed infantry who are largely in trenches and makeshift bunkers. If you're referring to any other use of nuclear weapons then it's suicide for everyone involved.