Usually, you would use the Windows Credential Manager for this (they are securely stored.) You can have a look at the
System.Credentials namespace (e.g.
Get Secure Credential).
If you are using Orchestrator, you can also manage your credentials Orchestrator-side as
Credential Assets (e.g.
Finally, there is the legacy
Get Password activity which keeps the password encrypted inside the xaml, but you will not be able to run it on any other machine. It is seldom used nowadays, but it is still there.
Note that since you have access to basically all of .Net, you can very well use
Invoke Code to implement your own encryption in VB if it can better fit your needs: