Find out your company code. To know your company code from the toolbar click Setup→Company. From the general section click Company Profile You can find your company code there.

Stop tomcat.

The name of your logo file should be of the form company-code.gif or company-code.jpeg or company-code.png. For example, if your company code is abccompany_com then the name of the logo file should be abccompany_com.gif (or .jpeg or .png). Now put this file in directory created in the previous step i.e. psa_x.y.z/webapps/psa/images/logos

Start tomcat.