Creating Custom Variables

In Process Builder, open the process file that you want, and then click Options in the left navigation pane of the Administration tab.
In the Custom Global Variables area, click Add Variable. A new variable is added to the Variables list.
Select the new variable in the Variables list.
In the Name field, enter a name for the variable.
In the Value field, specify the value for the variable. Alternatively, use one of the following options:

Click Import to open the Open File dialog, and then browse to and select a file that contains the values that you want to be assigned to the variable. When you click this file, its contents are imported into the Value field.
Click Export to open the Save File dialog so that you can save the contents of the Value field as an external file. You can save the value as a new file or replace the contents of an existing file.
Click Edit variable value to open the Value for <variable> dialog, where you can edit the value of the variable.