I would like to know the terminal commands to add *new* custom browser to Preferred Applications?

I don't mean selecting a browser using:

```
sudo update-alternatives –config x-www-browser

```

I would appreciate it if someone could help me with the following:

What are the Terminal Commands to add a NEW custom browser to Preferred Applications?

I would like links in other files to work as well, for example, when I click on a link in a `.pdf`, I am currently getting the following error:

```
Failed to execute child process "/opt/iron-linux-32/iron" (No such file or directory)

```

I also tried:

```
$ /usr/share/iron/iron
Failed to execute child process "/usr/share/iron/iron" (Permission denied)

```

It also failed when I elevated permission.

I have tried:

```
sudo gnome-default-applications-properties

```

Then, in the "Command" box entered:

```
/opt/iron-linux-32/iron %s

```

(with and without the `%s`)

I have also tried:

```
/usr/share/iron/iron %s

```

I am using Ubuntu 10.04. I want to use SRWare Iron.  

Note: There might be an issue as well with privileges.

I am using this as an opportunity to learn how to use the command line, and am really stuck. Seems like it should be possible, but I might be getting stuck on syntax.