You can easily publish your iPhoto library photos to your Flickr account. All you need to do is, setup your Flickr account in iPhoto and then select photos and publish.
Setup your Flickr Account:
- Choose iPhoto > Preferences, and then click Accounts.
- Click the Add button (+) in the lower-left corner of the Accounts pane.
- Click Flickr and then click Add.
- Click Set Up and follow the onscreen instructions.
- On the iPhoto Uploader page, click Next (below "If you arrived at this page because you specifically asked iPhoto Uploader to connect to your Flickr account").
- Click "OK I'll Authorize It."
Publish your photos to Flickr
- Select the photos you want to publish.
- In the toolbar, click the Share button, and then click Flickr.
- Click the set (what Flickr calls an album) you want to add your photos to, or click New Set. You can also click Photostream to add your photos to your Flikr Photostream.
- If you selected New Set, type a set name in the Set Name box.
- Choose an option from the "Photos View-able by" pop-up menu and an option from the "Photo size" pop-up menu.
- The size you choose depends on whether you expect your viewers to download and print your photos.
- Click Publish.
- To view your published photos, click your Flickr account in the Source list (below iCloud).