How to expand k-safe / fault tolerance from 0 to 1, i have expand vertica db from 1 to 3 nodes ?

On an EE mode database, you'll need to create buddy projections to increase k-safety. The easiest way to do this is to run DataBase Designer (DBD) in admintools or Management Console to build a design with K-safety 1. K-safety will be increased when the new design DDL is deployed.

In addition, after you expand K-safe from 0 to 1 and before nodes are taken down,
Please consider to verify that your DB configured as K-safe = 1, and all projections have a buddy projection.
Select * from system; --> Check the current_fault_tolerance of the DB.

If your cluster is configured with KSAFE=0 consider to use DBD in admintools like Bryan already suggested,
Or: SELECT DBD_ADD_NODES_REBALANCE_DATA(1);
The above API will create the required buddies, refresh them, rebalance if necessary
and will also mark the cluster to K-SAFE 1 (from 0).
Please note that this can take time and consume more disk space to create all buddies.
BTW, dbd_add_nodes_rebalance_data is not needed in Eon mode.