Upload 'flickr-slideshow-wrapper.php' to the '/wp-content/plugins/flickr-slideshow-wrapper' directory
Activate the plugin through the 'Plugins' menu in WordPress
Customize the settings under /Settings/FSSW/
For your convenience please use [set_id=XYZ] and/or [slidef=XYZ]. This is even the better choice as the code is not destroyed by switching from visual to html view (I'm mainly using html view only ;-) ). If you chose not to use [set_id=XYZ] and/or [slidef=XYZ] you shall continue to read about the following caveats:
Place <set_id="123213231231231"> from your flickr.com set into your content. Please pay attention to put the coding into the HTML section (HTML view).
You can call as well a slideflickr.com slideshow by putting the slideflickr id into <slidef="XYZ">
With <set_tag="tag1, tag2, etc."> your are able to compile your own tag-based set from flickr. Please refer to idgettr.com to get the relevant information.
Please be informed that slideflickr needs the same width and height values you defined during creation of your slideshow on their webpage - otherwise you'll see an endless loading bar.
Ensure that you have put the code into your html section of your blog, not the visual one! Again, using the shortcodes  is the recommended way to go.