Adding SSH users

I have just purchased some software for my server. The company is a reputable company and offers free initial installation of the software on my server. They state they need SSH access (for advanced trouble shooting), FTP, and an empty database.

My question is in regards to SSH access. When I login to WHM, I see there is a feature called "Manage Wheel Group Users", however, how do I create a user to add to the group?

I contacted my host. They stated to create a new account. That was all. They stated they do not give tutorials on SSH. I am not asking for a tutorial on SSH, I am asking for help on creating a username via WHM to be used for SSH.

The only "create account" I see is under "Create New Account", as in to create an account for a hosting package. After doing such, I do then have a username to "Add" to the group, however, when creating an account, I have to input a domain name. I have tried putting in a false one. This does not seem as if it would work. When I login via SSH with that username/password, I only get access to that fake domain hosting account I input.

How can I create a username that will have access to my main site domain. In addition, is there a way I can limit what a connection will do? The company has given me the IP address they will be connecting from. Therefore, can I specify what permissions a particular IP connection can have? I noticed there is a feature called jailhouse. Is this it?

BTW, I don't exepct a full tutorial on SSH. However, if one does know of some good tutorials on SSH, please post them. I am more than willing to read.

Thanks