Update README.md

Author: prerthan99

docs/README.md

@@ -1,20 +1,62 @@
 # User Guide
 
-## Features 
+## Features
 
-### Feature 1 
-Description of feature.
+### Add tasks
+
+You can add tasks of type **Todo** (which only has a description) **Deadline** (with a single date-time group as the deadline), or **Event** (with two date-time groups as the start/end instants respectively), using the `todo`, `deadline`, and `event` commands respectively.
+
+### List tasks
+
+You can list tasks using the command `list`. 
+
+### Delete tasks
+
+You can delete previously-added tasks using the `delete` command. 
+
+### Find task
+
+You can find tasks using keywords, with the `find` command. 
+
+### File output
+
+The task file is saved as a `.csv` for easy viewing in <kbd>Microsoft Excel</kbd> and other spreadsheet programs. 
 
 ## Usage
 
-### `Keyword` - Describe action
+### `todo <what is to be done>` — Creates a To-Do
+
+Creates a To-Do, set by default as incomplete. 
+
+### `deadline <what is due> </by | /at> <due date/time>` — Creates a Deadline
+
+Creates a Deadline, set by default as incomplete, with the due date/time as given.  _Some_ natural date-time groups are accepted (but some are still buggy):
+
+- `24th Feb 2020`
+- `Monday 5 pm` (buggy, as this goes to the *current* week's Monday, and not the next)
+- `11:40`, or `4:20pm`, or `12am SGT`
+- `11/2/2020` or `22/7/2020` or even `14-3-2020` (European format: `dd/MM/uuuu`)
+- `tomorrow` is not legit.
+
+> Example use:
+>
+> - `deadline return book /by 7 pm`
+> - `deadline complete CS2103T iP /by Tuesday 18/2/2020 23:59`
+
+### `event <event name> /from <start instant> /to <end instant>` — Creates an Event from `start instant` to `end instant`
+
+As for Deadlines, natural dates/times are accepted, and the same bugs apply.
+
+### `list`
+
+Lists all the tasks.
 
-Describe action and its outcome.
+### `find <keyword>` — Finds tasks
 
-Example of usage: 
+Finds all tasks that have a detail which contain `keyword`.
 
-`keyword (optional arguments)`
+> Example of usage: `find book`
 
-Expected outcome:
+### `delete <task number>`
 
-`outcome`
+Deletes the task at the given `number`.