Here you need to select an operation to perform.
If you wish to unpack contents of RAR, ZIP or other archive, choose "Unpack an archive" option. For example, you need to select it to decompress a file downloaded from Internet.
If you need to create a new archive and place some of your files in compressed format to it, choose "Create a new archive" option. It may be useful to compress files before sending them by email or copying to external disk. It helps to reduce the file size.
If you wish to add files to already existing archive instead of creating a new one, select "Add files to already existing archive" option.
After you have chosen an operation, press "Next" button at the bottom of dialog. If you selected "Create a new archive" or "Add files to already existing archive" option, you will be prompted with "Select files to add" dialog, where you need to select those files, which you wish to compress. In case of "Unpack an archive" you will go directly to the next "Choose the archive" dialog.