Hi @Lavinia,
You could send a private message to a user in the community forum as follows:
Option 1: Sending a private message
Step 1: Select the Reply
button as boxed in red below.
Step 2: Select the Reply
button once again, but now from this place, as shown in the image below.
Step 3: Now select New Message
as shown in the image below.
Option 2: Sending a private message to me
Step 1: Click on my username Kal_Lam.
Step 2: Then on the right, click the Message button.
Step 3: Type in your message.