MySQL DB Replication
Setup master-slave replication between DB1 and DB2.
APP1 reads and writes to DB1.
APP2 reads from DB2.
APP2 writes (if it does) to  DB1.


Note that APP2 will read eventually consistent data and it will have to handle writes to DB1 itself. (I do not tend to like master-master replication setup and writes to both ends due to past experiences but it is also an option.)

You said no links but below this link includes steps for setting replication, you might want to refer.