Slic3r is an open source program that is quite powerful and has many options that an experienced user can put to good use. It also provides a new user with an intuitive interface.
We highly recommend reviewing the manual provided by slic3r
After downloading the program go to File>Preferences select expert mode to access all the settings.
The configuration files for slicer are located on this page, after downloading them select File>Load Config Bundle to import all of the files into slic3r.
You will need to input your z-offset in the printer settings tab.
We regularly update these settings check back to confirm you have the latest version. It is also advised that you export and save your current configuration bundle since some of the defaults that you have setup will be overwritten if you have used the same setting names.