It is said by a guy who is bullying another one by twisting his hand. Is it related to Kansai dialect?
It has nothing to do with a dialect.
「よっとな」 is just one of the many versions of the shouts (chants?) people use as they make a physical movement of some sort such as lifting up an object, pushing or pulling an object, handing or tossing an object to another person, etc.
Similar versions include:
All of these mean "Here we go!", "Like this!", "One, two, go!", etc.