The exclusive gateway allows a document to be routed to different steps, depending on a condition, hence also called conditional routing.
In the screen below, the document will be routed either to the Approval step or to the Validation step.
Click on the arrow the condition is set for, then click on the settings icon as indicated in the screen below:
In the settings screen, choose the Condition Field and in the equals field, the string the Condition has to match.
For example, if the condition field 'VendorID' is set to 'Equals' to '1234', then documents that have the index field 'VendorID' with the value '1234' will be routed along this path.
If you do not set a value for an arrow, this will be the default flow if non of the other conditions are met.