xampp 1.8.3-4, set permission problem.

[lim]

hardware:
mac os x version 10.6.8

installed:
xampp 1.8.3-4

app:
bitnami wordpress module.

suggested:
root privilidges. how to ?
superuser to execute installation. how to ?

problems encountered:
error changing permission to 040755 in/ application/ xampp/ xamppfiles/ img
unable to set permission.

help and assistance is greatly appreciated.