We officially supported add-ons in Orange 2.6. You should start by checking the list of available add-ons. We pull those automatically from the PyPi, which is our preferred distribution channel. Try to install an add-on by either:

• writing “pip install ” in the terminal or
• from the Orange Canvas GUI. Select “Options / Add-ons…” in the menu.

Everything should just work. Writing add-ons is as easy as writing your own Orange Widgets or Orange Scripts. Just follow this tutorial and you will have your brand-new Orange add-on on PyPi in no time (an hour at most).