If customer language preference is known at lead creation, that can be set using the Language Preference dropdown on the lead creation page.
If language preference needs to be updated later, go to the customer page and click the pencil icon next to the name to go to the Edit Lead Details section. Change the language preference to Spanish using the dropdown menu.
If the correct agreement is not populating, an admin can check the EPC settings by going to Your Roles > EPC > Settings. Set "Contracts: Allow language" to yes. Save settings to apply.