If you are expanding your ceph cluster with extra nodes. You will need to prepare the node to have ceph installed and prepare the OSDs to be part of the ceph cluster. In order to do this, you can use ceph-deploy to install ceph on the new nodes and prepare/activate the osds on it. The procedure is pretty straightforward.
On the new node, first create the ceph user and enable key-based login to it.
On the node where you have ceph.conf available (normally the node you deploy from ) cd into its directory and execute the following as ceph user
ceph-deploy install #Newnodename
ceph-deploy prepare #Newnodename:#Osdmountpoint
ceph-deploy activate #Newnodename:#Osdmountpoint
You can verify that the new OSDs are active via
ceph osd tree
If the OSDs are showing as down and out of the cluster. You can add them in and bring them up them using.
ceph osd in osd@#ID
systemctl start ceph-osd@#ID
The above two commands are to be executed on the new node