Hi @SanchezNuñez!
As @KenBuja demonstrated, there is a Title option in the Pop-ups settings box. You can either add a static title to this box, such as the layer name (ex: "Roads of Alaska") or you can make the title dynamic, where it changes from feature-to-feature like what Ken is showing in his image. To do this, click the { } box next to the Title textbox and select the field (or fields!) you want to populate the title. In Ken's example, he has static text ("My layer: Site ID") and then a dynamic element ({FIELD_ID}). The dynamic element notes the Site ID of whichever feature he has clicked on. In this case, it was site 6566.
Let me know if you have any questions!
