KEGG files can't be imprted into SimBiology as is. You will need to convert them into SBML files first.
There are converters available to do this. for instance KEGG Translator. That being said, the resulting SBML file will contain the model structure but no kinetics because it's not contained in the original file. So you will need to define them to run your model.
May I suggest you to have a look at the Biomodels repository? It contains curated, runnable models which have been published and that you can download in SBML format and import in SimBiology.