The notation for a use case diagram is pretty straightforward and doesn't involve as many types of symbols as other UML diagrams. You can use this guide to learn how to draw a use case diagram if you need a refresher.
Learn what is use case diagrams and how to create a use case diagram with this comprehensive guide with use case diagram examples and editable templates.
To draw a use case diagram in UML first one need to analyse the entire system carefully. You have to find out every single function that is provided by the system. After all the functionalities of a system are found out, then these functionalities are converted into various use cases which will be used in the use case diagram.