To write the expressions, you will need to follow the syntax as explained here.
If your expressions are a little complex, you can take recourse to our Conditions Generator tool.
How to Use Conditions Generator
Using the conditions generator tool is not tricky at all. All you have to do is fill and select the fields wisely.
Choose the Field Type of the field for which the condition is based
The ID of the field
Comparison type for the condition
Choose whether the value is based on a text value, numeric value, or value of an another field
Write the value
Use OR to add more conditions that are OR connected
Use AND to add more conditions that would be AND connected
You can retrieve the expression above the conditions generator
You can further use the "OR" or "AND" button to write conditions that are "OR connected" or "AND connected".
You can use OR operator to write multiple conditions which then would be OR connected. Writing expressions in separate lines will be AND connected by default.
You can see the expression result above your conditions.