I can't run simple example

when I run, can’t open the file vis.mac
What can I do?

Difficult to diagnose without more information. Did you follow the installation and application building and running instructions? What, exactly, did Geant4 print before saying it couldn’t open vis.mac?

Most likely this is because your working directory, i.e., the directory/folder you’re currently working in, whose files show up when you list them (“ls”) and from which you have launched your Geant4 application, does not contain vis.mac. Probably because you are not in the appropriate working directory. An essential skill is to understand the concepts of directory, working directory, how to change working directory, etc.