This is the 533rd most frequent German word.
personal
"Personal" in German means "staff" or "personnel."
Here, 'Personal' is used as a noun meaning 'staff' in a general sense.
Das Hotel sucht neues Personal für die Rezeption.
The hotel is looking for new staff for the reception.
The word 'personalisierte', derived from the same root, means 'personalized' and is used as an adjective to characterize the noun 'Nachricht' (message).
Ich schreibe meiner Freundin eine personalisierte Nachricht.
I am writing a personalized message to my friend.
In this sentence, 'persönlichen' is an adjective derived from 'Personal', modifying 'Gebrauch' (use) to mean 'personal' in a private or individual sense.