You can manage your access to WMFLabs instances via your preferences on this Wiki. Under the "Open Stack" tab, you manage your public SSH keys (dsa or rsa).
|Caution:||The public key is always the file with ".pub" on the end. Always keep the private key in secret and never share with anyone else!|
After you have uploaded your new public key here, puppet will propagate your keys to all the projects that you have access to (note: this may take a couple of minutes). Then you would be able to access the instances in those projects.