The Tutorial

1. Go to the Advanced Customization area of Dreamwidth.
2. Click on the link under "Advanced Options" that says Your Layers.
3. Look toward the bottom of that page and you'll see this:
   
4. Under the "Create top-level layer" is where you will start. From the "Type" drop down menu, choose Layout and from the "Core Version" drop down menu, choose 1. Choosing Core 2 won't let this work, just so you know. So it'll look like this:
   
5. Hit "Create" and it'll make the new layout. Since I already installed Flexible Squares and Smooth Sailing, I'm going to use Mixit for this tutorial but it should work for all the layouts as far as I know. :)
   
6. Click on the "Edit" button and it'll take you to another screen that looks like this:
   
7. UPDATED: Because Livejournal made changes to the raw source code for each of their layouts, the way the tutorial was originally written will not work.  I have linked the source code for four layout bases, but do not have the others. I'm sorry for any inconvencience they may be to people, but hate the system, not the writer of the tutorial.
8. Here are the Source Codes that will work with the rest of this tutorial: Flexible Squares | Smooth Sailing | Mixit | Nebula

If you are looking for any other layout styles, I'm sorry, they are not available here and I'm not good enough with coding to be able to make them work as well. I apologize for any inconvenience this makes, but by the time I realized I had to provide the code, it was already too late to salvage the others! :/

9. Copy all of the code. Using the Select All (keyboard command Ctrl+A) and just copy it (keyboard command Ctrl+C). Now you want to paste it into the layer window in your other tab. Click "Save & Compile" at the top of your window.  There should be no errors.
10. Now go to the Your Layers again and you'll see that it now lists your layout! Yay, now, that's the hard part and everything now should be easy as pie. Well, hopefully...I think? Yeeeah.
    
11. Now go to your Customize Journal Style page and to make life easier, click on the Your Custom Layers link under the "Select a New Theme" area.
    
12. Choose the layout you want by click the button that says "Apply Theme", so I'm going to pick Mixit, because that's what I want to mess with. It'll automatically apply the layout to your journal.
13. WE'RE NOT DONE YET! Keep reading kids. :P
14. Click on the Customize link and it'll take you to a very similar page that looks pretty much what you had on LJ.
    
15. I'm going to use this layout by thefulcrum for this tutorial. Go to the Custom CSS area of this page.
16. Uncheck the box that says "Use layout's "Base Weblog" stylesheet" because you don't want to use that.
17. Paste the code from the layout you want to use into the large textarea.
    
18. Hit the "Save Changes" button.
19. You are done.

Things to Note

• If you don't use CSS for your layout, you won't have a layout, it'll just be Times New Roman text without any special format. Boring boring, yes, but that's life, unfortunately.
• Flexible Squares is a little limited and I'm trying to figure out how to not make it so. Basically, layouts from people like milou_veronica might not look as nice because you can't cut down the list of navigation links (such as getting Memories and your website removed from the list in the menu).
• If you're using someone else's CSS, please, oh please remember to give them proper credit. :)
• If you intend to add any modifications to your "layout" layer (not the "theme" layer!), please make sure to follow the instructions here so everything shows up all right.