Download an artifact from Nexus to Jenkins
There are a few ways to do this, but by far the easiest is to put your credentials (either username/password or ssh keypair) into the Jenkins built-in credentials store and then use the sshagent step in your Pipeline script:

sshagent(credentials: ['my-credentials']) {
  sh('scp mynexus.com/my_artifact.zip ~/my_artifact.zip')
}


You may need to install the SSH Agent plugin to be able to use this step; I'm not sure if it's part of the default set of Pipeline plugins or not.