Install Cacti on Debian for dummies

Hi all,

I want to install cacti (frontend to RRDTool) on my Debian 6 VPS.

My dummy questions please...

The requirements include RRDTool and net-snmp so is there a way to check these are properly installed?

Re the command
After logging in to my VPS in putty do I need to change directory before I run this command ie to say where this should be installed?

Thank you :)