You can import standard steel sizes. In AC19 go to Options > Import standard steel profiles and select New Zilland in the country code. Select the profiles and sizes you want and "Add profile to the project". In AC20 its Options> Complex Profiles > Import... Use these with Complex Profile beams.
For future reference add your AC version and OS (Mac or Windows) to signature in your forum profile (link at top of forum page) as answers can vary depending on your setup.