If you are using WP-SimpleViewer (the dedicated SimpleViewer plugin for WordPress), instructions for use can be found here.
If you want to manually embed a SimpleViewer gallery (perhaps one that you have created in svBuilder-Pro) in a WordPress page or post, you can upload the complete gallery folder to your web server and then embed the gallery using the baseURL method of embedding documented here.
Just make sure, when entering the embedding code into the body of your page or post, that the method of entry is 'Text' rather than 'Visual'.
If you continue to experience difficulties, please post the URL to your gallery so that I can take a look and help further.
I've also tried using Picasa albums and just get 'no images specified in gallery xml'.
This sounds like you may have entered an incorrect Picasa User Id or Album Name into the WP-SimpleViewer gallery settings window.
To test the functionality of the Picasa Web Album source, try entering:
Picasa User Id: picasateam
Picasa Album Name: VegasWeekend
SimpleViewer Support Team