The View menu

This is the menu where you can choose what is displayed, and where. The first two items are Show Terminal Emulator and Show Command-line; more about these here.

The next three determine how the panes are orientated, and how many are shown. Panes come in pairs. The one on the left of each pair shows only directories (the dir-view). When you select one of those directories, its contents (both files and immediate subdirectories) are displayed in the other, righthand pane (the file-view). By default 4Pane has (believe it or not) four panes showing, split vertically; dir-view, file-view; dir-view, file-view. However you can choose instead for the split to be horizontal, with an upper pair and a lower. Or (despite the name) to unsplit, so that only one pair shows; this is useful when you want to be able to see more file-view columns at a time. You can change the display type at any time, using Split Panes Vertically, Split Panes Horizontally and Unsplit Panes.

Sometimes useful are Replicate in Opposite Pane, which duplicates the current twin-pane's filepaths on the opposite side; and Swap the Panes, which swaps one twin-pane's selection with the other.

The next menu item is Filter Display, which allows you to restrict what is displayed in the currently-selected pane. See Filter. Following this is Hide Hidden dirs and files (or, if they're already hidden, Show), which also applies to the currently-selected pane. You can set the global default in Options > Configure 4Pane: Display > trees.

Last is Columns to Display, which opens this submenu. Here you can choose which columns the current file-view should display: time, owner etc. As you'd expect, you can sort a file-view by clicking on a column header; for example, to sort by size, click the size-column header.