Visit the Horde website, and find the link to the latest release. SSH to Dreamhost backend and download the release on to your server:
wget ftp://ftp.horde.org/pub/horde/horde-latest.tar.gz
tar -xzf horde-latest.tar.gz
mv horde-webmail-1.2.3/* ../horde
Setup PHP.ini and PEAR and create a database in your Dreamhost control panel, and have an email account ready (in this example, me@example.com).
Run the setup script on the SSH console. I was not getting anything on the command-line, just the option to type, then I realised I was using the wrong php command. It should be: /usr/local/php5/bin/php scripts/setup.php.
Chose the following options:
- URL (I use a subdomain): /
 - Configure database settings: 1
 - Database backend: mysql
 - Not persistent: 0
 - Connect: tcp
 - DB host: mysql.example.com
 - Default port (enter)
 - DB name
 - Default charset (enter)
 - Use SSL: 1
 - Default Certification Authority, Split reads (enter)
 
Then:
- Create database or tables: 2
 - Create database: n
 - DB username, password
 
Then:
- Configure admin settings: 3
 - Existing mail user: me@example.com
 
The final, important task was to change the value of 'server' in $servers['imap'] in horde/imp/config/servers.php from localhost to your mail server, mail.example.com.
One additional task was to connect my N95 with the server. Beware, before you start syncing make sure you have your locale setting correct in Horde (Options > Global Options > Locale and Time), otherwise you’ll get duplications. To set up in the N95 Sync profile:
Host address: horde.example.com/rpc.php
In order to install other packages/applications/projects (whatever they’re called), go to the CVS snapshots, at http://ftp.horde.org/pub/snaps/ and find the link to the tar gz and wget it to your server.