How do you add sources to your installer after the initial jailbreak? I will show you step by step how to do this via screenshots.
Make sure you’re WiFi, 3G or EDGE connection is on.

1) Start Installer 4 by tapping its icon.

2) Click on “Sources” once the app has started.

3) Select the “Edit” button and press the “+” symbol.

5) Type a Source (eg i.modmyfone.com/).
Press “Done” when you’re finished and wait for the source to be refreshed.

Now you will be able to download packages from that repo and any packages they will release in the future.
How to remove a source when it’s no longer working?

1) Open installer, go to sources, select edit.

2) Then press the - sign for the source you would like to remove.
A delete button will show, and so you can delete the source.

Now your done!