Make sure your new validator node is fully synced and is running with the new signer address.
Change the signer address
This guide refers to your current validator node as Node 1 and your new validator node as Node 2.
Log in to the staking dasboard with the Node 1 address.
On your profile, click Edit Profile.
In the Signer's address field, provide the Node 2 address.
In the Signer's public key field, provide the Node 2 public key.
To get the public key, run the following command on the validator node:heimdalld show-account
Clicking Save will save your new details for your node. This essentially means that Node 1 will be your address that controls the stake, where the rewards will be sent to, etc. And Node 2 will now be performing activities like signing blocks, signing checkpoints, etc.