diff --git a/README.md b/README.md
index 77977f6..f598831 100644
--- a/README.md
+++ b/README.md
@@ -6,6 +6,14 @@ Monitors various aspects of a Mailcow instance:
 Email domains with quota usage, number of mailboxes, number of aliases
 Mailboxes with quota usage, number of messages, last logins via IMAP/POP3/SMTP
 
+You have to create an API Key for the MKP to work. Login to your Mailcow instance and go to
+
+System|Configuration
+
+Take a note of the section API, expand it and activate "Activate API" within the section "Read-Only Access"
+
+Don't forget to insert the IP of your CheckMK instance within the textbox "Allow API access from these IPs/CIDR networks".
+
 ## Caveats:
 Tested only with dockerized versions of Mailcow
 Tested with Mailcow version 2022-07a and higher