Document icarus.

README.md

@@ -1023,6 +1023,8 @@ The dialog has a tab for each main category of options:
         won't cause problems,
         but means you can't fix incorrect manifests
         generated by the current version of icarus.
+        See also the "Create Manifests" option in
+        [the icarus Settings dialog](#the-icarus-settings-dialog).
 
 The Cheat Editor
 ----------------
@@ -1228,12 +1230,63 @@ closes the file-system browser without selecting anything.
 The icarus interface
 --------------------
 
-TODO
+When launching icarus,
+directly or by picking "Import ROM Files ..."
+from higan's [Library menu](#the-library-menu),
+the main icarus window appears.
+This is [a filesystem browser](#the-filesystem-browser),
+with customisations:
+
+  - The filesystem browser only lists
+    files with extensions typically used for ROM dumps from
+    consoles higan emulates,
+    plus `.zip` files since ROM dumps are often compressed.
+  - Each matching file has a check-box next to it.
+  - You can tick the check-box next to every file at once
+    by pressing "Select All" in the bottom-left.
+  - You can un-tick all the check-boxes
+    by pressing "Unselect All" in the bottom-left.
+
+Pressing "Settings ..." in the bottom-right
+opens [the icarus Settings dialog](#the-icarus-settings-dialog).
+
+Pressing "Import ..." in the bottom-right
+will close the filesystem browser
+then try to import all the files
+whose check-boxes are ticked
+into [the Game Library](#the-game-library).
+icarus displays a progress dialog during the import process.
 
 The icarus Settings dialog
 --------------------------
 
-TODO
+The icarus Settings dialog contains the following settings:
+
+  - **Library Location** determines
+    where icarus puts the games it imports.
+    See [Moving the Game Library](#moving-the-game-library)
+    for details.
+  - **Create Manifests** causes icarus
+    to write out a manifest file describing
+    each imported game
+    to that game's [game folder](#whats-in-a-game-folder).
+    This means that higan doesn't have to regenerate
+    the manifest each time an imported game is loaded,
+    but it means that a future version of higan
+    with an incompatible manifest format
+    may be unable to play these games.
+    Note that higan also has an "Ignore Manifests" option
+    in the Advanced tab of
+    [its Configuration dialog](#the-configuration-dialog).
+  - **Use Database** causes icarus to use manifest information
+    from its database of known-good manifests,
+    if it's importing a game it recognises.
+    For unrecognised games,
+    and for all games if this box is unticked,
+    icarus gueses the manifest data.
+    This option is still relevant when "Create Manifests" is unticked:
+    higan uses icarus to generate a manifest when a game is loaded,
+    not just at import-time.
 
 The Game Library
 ================