Before you Delete the User Account please follow below steps

Step 1: Suspend User Account

Step 2: Change User status to Resign

Step 3 as below

1. From Main Dashboard go to Common Data  and select Setting 

2. Go to

3. Select User with status Resigned OR by Search User Name

4. Click on Delete button

Important Note: After performing this action, you can't find the User in your User Library anymore.