WP RSS Aggregator gives you the option to import the feeds you had in other readers, such as Google Reader, into WP RSS Aggregator (and hence, your website). You can therefore easily use the plugin to create your own self-hosted aggregator.
The first step is that of entering your feed sources. To do this, head over to the Tools > Import page in your WordPress dashboard.
Click on the Choose File button, and select the OPML (with the .xml extension) file you have on your computer.
Finally, click on the Upload file and import button and the feed sources will be imported into WP RSS Aggregator.
You will find them listed in RSS Aggregator > Feed Sources. They will adopt the general settings.