The filter dialog box, as shown below, is split into three sections, each of which is explained below the image.
The number below correspond to the image above
1. Filter Name - First of all enter a name to help identify the filter.
2. Conditions - The conditions section is where you can set the parameters this filter to abide by. You will be shown all the available options to start with, from Subject to the size of the email.
First thing to do is to choose whether you want to enforce this filter when ALL the parameters match or ANY of the parameters match.
Secondly you have to choose the parameters. Simply check the box next to the parameter you want to include and then change the settings for that parameter accordingly. There are three good examples of how to set up filters in the manual, click here to go to the examples.
If you want to add a new condition (you may want to add various subject conditions for example) click the add condition link shown at the bottom of section two in the image above.
3. Actions - The actions section is where you choose how to deal with any email that meets your new filter. You can choose to set the email(s) for deletion, add the sender of the email(s) to the white or blacklist and set the filter to override your white list. A combination of these settings can be used to, for example you could set every email that matches your filter to be set for deletion, add the sender to your blacklist and have it override your white list.
Once your filter is setup click the ok button.