Welcome to MR. I hope you love your new 350.
IMO the best place to get free books is right here on Mobile Reads:
https://www.mobileread.com/forums/ebo...&sort=dateline
Any BBeB/LRF or EPUB book will work.
To get the books on your reader, you can use a lot of different methods. I personally prefer the Sony Library software. You add books to your Library using the File menu "Import Book" option.
The library is set to sync all books to your 350 automatically.
Optional: you can add titles to "Collections" by:
1. click the plus button at the bottom left of the software
2. name the collection
3. drag titles from the Books category (which lists all books you've imported) to the Collection name in the left navigation pane.
If you want to sync only certain Collections:
1. With the reader connected, click the down arrow button next to the reader in the left navigation pane. The reader's collections display
2. click on the Synch listing under the Reader. You'll see checkboxes for each collection and type of content
3. click the boxes to turn on and off various collections, pictures, etc.
Hope that helps.