Update UG with CLI and how to guide

docs/UserGuide.md

@@ -64,6 +64,19 @@ the command-line interface (CLI).]
 
 ### How to use the command line interface (CLI)
 
+MediCLI is operated using typed commands to the command line interface (CLI). Do not worry if you do not understand CLI yet; Here we will explain to you the formats of text commands and how to use them.
+
+![Ui](images/cli_format.png)
+
+| CLI Format        | What it means                                                                                                                                                                                                                                                        |
+|-------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Command           | The command tells MediCLI what action you want to perform.                                                                                                                                                                                                           |
+| Index             | Certain MediCLI commands have an `INDEX` field, which is a number that is assigned to a particular patient, doctor or appointment. Index must be larger than 1 and can be up to the maximum number of patients/doctors or appointments as listed in the MediCLI GUI. |
+| Parameter Prefix  | Fields typically have a prefix like `i/` or `n/` followed by the field content. This tells MediCLI what field you are entering.                                                                                                                                      |
+| Command Parameter | The command parameter is the parameter prefix followed by field content. For example, the command parameter to enter NRIC would be `i/S1234567A`                                                                                                                     |
+
+<div markdown="span" class="alert alert-info">:information_source: **INFO**: Not all MediCLI commands have fields! For example, the command to clear all data is simply `clear`.</div>
+
 ### Initial start-up and sample use-case
 
 1. Type the command in the command box and press Enter to execute it. e.g. typing **`help`** and pressing Enter will open the help window.<br>