Using columns inside other columns can get, well, complicated. Here are some tips to help you get started. Along the way, you may find shortcuts that work better for you.
See the column layouts overview article. In particular, make sure you understand the concept of columns, module layers, and child columns.
You can create a new main column in by dragging a module to the right or left of an existing column. But when you create new layers in a vertical column, dragging in a module doesn't always create its own column. The safest way to insert child columns is to use Add content > Row layouts. In addition, with complex column layouts, it can be helpful to build the row layout first, then add the content. For example, here's a layout for three main columns (two on top, one below) in which the first column (on the left) includes a layer with four child columns and the second column (on the right) includes a layer with two child columns.
Once you have the structure set up, it's easy to drag in content modules, as in the following example.
Note that the first child column in the second layer on the right has two modules, the text and the small photo. If you move that column, the two modules will always move together.
You can still create simple column structure by dragging modules directly into a row, and you can move columns to create new structure. See the Related Articles for more information about inserting columns.
Click the Edit Column icon for a module, then mouse over Move Column --you'll see the scope of the column that module is in, as shown in this screenshot.
In some cases with a layer of columns, you'll find a module that isn't in its own column that you want to style individually. In this case, follow Tip #2 to drag in a row layout of a single column, then move that module into it. You may run up against the level of column nesting (see Tip #1) but may find another way to organize the column layers so you can get get the module into its own column.
When you mouse over Delete column, you can see the scope of what you'll be deleting. But since there's no Undo, it's even safer to delete modules first, then delete column structure. See the article about deleting columns.