Making sure I understand the process to lay a book out.

In your stead I'd go with InDesign if I were going to do this thing for several projects over the next couple of years. If it's only going to be a one-off thing, then settle for Scribus.

The basic procedure for doing book layout follows. These are in rough order, but in practice you end up working them in tandem for many reasons, not the least of which is the fact that everything influences everything else.

Edit the text of the book through a workflow that can end up in the layout program. In other words, check what sorts of text and styling mark-up your layout program supports and make sure your text ultimately can be converted to that form. Alternatively, do all styling and final edits of the text in the layout program. Do not skimp on proper, style-based editing; it is absolutely essential for modern text handling in your layout program. Pay attention to proper typography already at this point, it'll save you time if you work with the proper character set from the beginning, using the correct dashes and such, for example.
Choose the material factors for your book, such as dimensions, estimated page count and such. Find out how much text and art you're going to be handling. Create page designs that take these factors into account, and work purposefully for the book's intended usage style as well. Page design includes things like planning your layout graphics (graphical elements that exist on a page due to the layout paradigm and not because of some particular contextual relationship with the contents of a given page), text areas, white space, headers, footers, different page plans (for complex works you'll often want to display different sorts of data on differently arranged pages) and so on. Be aware of the visual lines and shapes that your choices form on the page; graphic design is, above all, about the unintentional and intentional tensions caused by positioning of functional elements.
Plan your typography to support everything that went before. Typography concerns the way you use the text space allotted in your page design: which typefaces you use, font sizes, typographical effects for text emphasis, captions, image captions, readability concerns (column width vs. font size and line spacing), baseline grid, and so on and so forth. It's important for typography to be consistent, so you're basically working on the basis of the styling you did
Once you have page models, typography and edited+styled text, you can start bringing the text into your layout. Control text flow, make use of the functions of your layout program, pay attention to consistency and responsiveness to changes; you're going to be making them anyway, so it's important that you can automate as much as possible to ensure that consistency. Make sure that the styles are consistent and that you know what your layout has eaten and why it looks the way it does.
When the text is in the layout and flows properly, bring in the illustrative imagery, their captions and other such floating (not anchored to text flow) content. Do not move or reshape your text boxes to accomodate the other material, but rather set those to flow text around them with appropriate settings (this is important to preserve that responsiveness to changes I mentioned above). This is also a good moment to start paying attention to pagination of your content: where pages begin and end, and how many pages each chapter of text takes.
Once you have everything together, you do visual edits. This is a many-faceted and complex phase, as you're basically grinding the work to fix everything that still remains unfixed. Example tasks include dealing with widow and orphan lines, removing whitespace patterns within text columns and hyphenation.
At some point you're presumably sitting on a finished book; ideally you'll also have found a printer for it then, but that's another story.

Hmm... I don't know how much help that is if you're completely clueless. I've been running unofficial layout courses for my indie designer friends lately, and usually it's been easiest to teach this stuff when they've had some concrete project to work on and apply their knowledge to. It'll probably make better sense once you start working on it.