Add note for duplicate person and appt

docs/UserGuide.md

@@ -367,6 +367,12 @@ _**Example:** `t/friend t/likes coding` has 2 tags and it is valid._
 - `add person n/Betsy Crowe t/friend e/[email protected] a/Newgate Prison p/1234567 st/recovered t/criminal` adds a person named `Betsy Crowe` with email `[email protected]`, address `Newgate 
   Prison`, phone number `1234567`, status `recovered`, and the tags `friend` and `criminal`.
 
+<box type="warning" light>
+
+**Note:** Ensure that you enter a **unique name (case-insensitive) and phone number** for the person you are adding. Else, it will be detected as a duplicate, and an error message will be shown. 
+
+</box>
+
 <box style="background: #eeeeee">
 
 **Navigate back to the subsections here:**
@@ -593,6 +599,13 @@ _**Example:** You will see `2024-12-10 12:30` displayed as `December 10, 2024, 1
 
 </box>
 
+<box type="warning" light>
+
+**Note:** Ensure that you enter a **unique person, date and time,
+and appointment type** for the appointment you are adding. Else, it will be detected as a duplicate, and an error message will be shown.
+
+</box>
+
 <box type="tip" light>
 
 **Tip:** You can decide to leave out sickness and medicine inputs when adding them, then edit them later.