The recommended and repeatable approach to access a server using SSH is to use a third party tool, PuTTY.

PuTTY

First download and install PuTTY - https://www.putty.org/ - and then please follow the steps below:

Generate PuTTY private key

1. Generate a PuTTYgen compatible key by running puttygen which would have been installed along with PuTTY. Go to Windows Start menu → All Programs → PuTTY→ PuTTYgen.
2. Click on the Load button beside 'Load an Existing Private File Key' and then load the training.pem file you should have been given.
3. Then click on 'Save private key' and save the file as training.ppk into a folder.

Open Connection in PuTTY

1. Run PuTTY - Go to Windows Start menu → All Programs → PuTTY→ PuTTY
2. Enter the remote server Host Name or IP address under Session in the following format ubuntu@<ip address>.
3. Navigate to Connection > SSH > Auth.
4. Click Browse... under Authentication parameters / Private key file for authentication.
5. Locate the training.ppk private key you saved above and click Open.
6. Finally, click Open again to log into the remote server with key pair authentication