UML: Sequence Diagrams [video]
Following video from Derek Banas’s Youtube channel provides overview of the UML Sequence Diagrams which you can use to design interactions between components of your application or interaction between application and the third party services.
There are different tools you can use for this but I will recommend to start with https://www.WebSequenceDiagrams.com/ — this online service provides great set of tools and its free tier is enough to start creating basic diagrams for your project.
UML 2 Sequence Diagrams
P.S. If you would like to view all UML 2 tutorials from Derek Banas, please follow this link.