You can find your custom fields in the contact card as the second tab right away. But first, you need to define your custom fields in the settings, which we show in the video below.
If you don't choose not to show the value in the table (meaning the contact directory) when setting up a new custom field, the values from custom fields will be all the way on the right side.
You can then tweak which columns are shown using the gear icon.
In the Settings module go to the Contact settings section. In this section, click Custom fields.
Then click on Add Field and pick the type of custom field (e.g. value, currency, long text, switch...) and start typing field names or, if needed, specific values.
We explain it in detail in this video.