One quick way of learning, with a familiar AC 9 file, is to just migrate that file to 13. In your Reference Guide, see the chapter called "Migration Guide for ArchiCAD 13".
Otherwise, in the Reference Guide PDF, read the Chapter called "Documentation", particularly the subchapter "The Layout Book".
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AC 27 USA and earlier • macOS Ventura 13.6.9, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB