You can use the left hand menu to filter on a metric of a slice by clicking the three dot menu and clicking "Add as filter".

You can also add a filter by clicking the filter icon below the question title.

To set the value for the filter you can use the drop-down for the value on the right side of the value.

To edit a filter, click on the desired pill below the question title.

Click on the drop down to change the value of your chosen filter attribute.

You can also change the operators by clicking the middle drop-down.

Make sure to click the 'Run Question' button once you add or change a filter to apply those changes to the question

You can also do OR filters and nested filters in Zenlytic. Just click "Add Filter" and then add filter rules or groups as needed to create the filter you're looking for.

Here's a video walkthrough of that flow.