In Bizagi, you may define the condition for the path either in the Gateway itself, or in each of its decision branches (or sequence flow).
To define the conditions to be met for the given path, open the Gateway properties and locate the Advanced tab.
For each of the outbound paths at the Gateway (i.e, .each decision branch), you will find a corresponding row in the Gates table, identified by the branch name (caption).
You may either define a conditional expression for the selected path, or designate it as the Default path.
Note the visual representation of a default path is a small oblique line crossing the decision branch.
Defining conditions for each sequence flow
To define the conditions which must be met for each path in a Gateway, right-click on the sequence flow representing the path.
In the options displayed you may easily set that this sequence flow is to be taken as the default path by clicking on Is Default (marking this property)
The Edit condition option provides quick access to the expression editor to create a condition for this path.