Not sure about the YanaR font, but if you are considering a Helvetica font and just want to install the font in a regular Helvetica, you would do:
buttonTitleLabel.font = [UIFont fontWithName:@"Helvetica" size:20.0];
To make the font bold, all you need to do is add -Bold to the end of the font name, for example:
buttonTitleLabel.font = [UIFont fontWithName:@"Helvetica-Bold" size:20.0];
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