You define conditions as was described in chapter Rule structure. In addition, the branching type that you determined when creating the step is displayed (See chapter Add and modify a user activity).

Split type in the condition of the routing rule
If your process branches into several steps, use branching type to determine the desired behavior. You can select whether one (OR) or several conditions (AND) must be met. Note that the branching type is only displayed here, you can only modify it in the step properties (See chapter Add and modify a user activity).