Please install Simple Newsletter Plugin – Noptin
Create new or edit existing newsletter form
and then add its widget to the footer 5th column:
You can check new subscribers in Email Subscribers tab
Noptin have also paid (unfortunately) addons for Mailchimp, ConvertKit, Campaign Monitor, ActiveCampaign, AWeber, Constant Contact, GetResponse, HubSpot, Klaviyo, Sendgrid, Sendlane, Sendy and many more.