To initialize your first todo file, invoke the command todo-show.
This prompts you for a file name (defaulting to the value of
todo-initial-file), prompts you for the name of the first
category (defaulting to the value of todo-initial-category),
creates and visits the file and displays the category in Todo mode, and
then prompts you to enter the first item. If you choose not to enter an
item now, simply type C-g, which leaves the category empty but
otherwise well-formed. If you prefer not to be prompted to enter an
item on adding a new category, disable the option
todo-add-item-if-new-category.
Once at least one todo file exists, invoking todo-show enters
Todo mode. Invoked with a prefix argument, the command prompts for
which todo file to visit. Otherwise, the first invocation of this
command after loading the Todo mode package visits the default todo file
(option todo-default-todo-file) and shows its first category.
(You can get a different display with the first invocation of
todo-show by customizing the option todo-show-first;
see Todo Categories Mode and Files of Filtered Items.)
If you leave Todo mode and later invoke todo-show to re-enter it,
by default this returns you to the current (i.e., last displayed)
category of the current todo file, which is the one in the most recently
selected and still live buffer visiting a todo file. If you disable the
option todo-show-current-file, then non-initial invocations of
todo-show always return to the first or current category of the
default todo file.
If you want to enter Todo mode and go directly to a specific category
instead the first or current category in the current or default todo
file, use the command todo-jump-to-category; Navigation,
for details. You can also enter Todo mode by invoking the command
todo-insert-item; Inserting New Items, for details.
The most convenient way to use these commands to enter Todo mode is to
define global key bindings for them in your init file. Good choices
are C-c t for todo-show, C-c j for
todo-jump-to-category and C-c i for
todo-insert-item, since these commands are bound to t,
j and i, respectively, in Todo mode.
You can leave Todo mode by typing q (todo-quit), which
buries the current todo file buffer. Doing this also saves any changes
you have made to the file, and leaves both the file and the category
that was displayed on quitting current for subsequent Todo mode commands
(unless the buffer made current by quitting is visiting another file and
category in Todo mode, in which case the latter become current for Todo
mode commands).