You have as first steps in installing on Ubuntu
1. go to System Menu > Software Sources > Third-Party Software;
2.click add and paste this line in:
ppa:sunab/kdenlive-release

on my 10.04 I have to do:
1. go to System Menu > Administration > Software Sources //Enter sudo password// > Other Software;
2.click and paste this line in:
ppa:sunab/kdenlive-release
click
then after I relaoded Synaptic and entered "sudo apt-get update && sudo apt-get install kdenlive" in a terminal I got(at the end of a lot of Hit...s:

E: Could not get lock /var/lib/dpkg/lock - open (11: Resource temporarily unavailable)
E: Unable to lock the administration directory (/var/lib/dpkg/), is another process using it?

you forgot to tell me to close Synaptic after the reload!

But Where is the program? How do I start it?
The Quick start guide says "When you first start Kdenlive, you will have..." But HOW DO I START KDNLIVE?

For the lock, try
sudo apt-get update
sudo apt-get install kdenlive
in the terminal, without the &&, since apt has changed something there and seems to try to do things in parallel where it should not.

Or was it Synaptic only?

To run kdenlive, enter
kdenlive
in the terminal. (Or via Alt+F2, or via the menu if you find the entry.)

And thanks for the hint, I updated the download page.

Simon

Hope Gregor doesn't mind me adding something here?

Simon - I followed these instructions exactly using a fresh install of 10.04 and all the h264 rendering options have red crosses by them.

This is an old issue for me - I've been running KXStudio simply to get a working Kdenlive with h264 available - but I'd love to know how to fix this issue in 10.04 from the point I am now at. Is there a simple step-by-step fix, or am I better sticking with KXStudio?

I'm not sure what the best way is for Ubuntu — other guys here can help you better. Perhaps it works with ffmpeg from the sunab repository, or by compiling ffmpeg yourself. Best might be to wait for someone who really knows this :)
(Another how-to here)

Simon

Thanks for those links - the first one looks like something I feel confident in trying. I'll give it a go!

[later] - Ok I gave it a go! During the sequence of steps, Kdenlive itself (with the unavailable h264) was removed. When I reinstalled Kdenlive after completing the sequence, h264 was still unavailable unfortunately.

Open to any further ideas anyone may have.

getting H264 support in ubuntu is explained here: http://www.kdenlive.org/forum/kdenkive-078-packaged-ubuntu-maverick-lucid-karmic-jaunty

A restart of Ubuntu gave me the program entry in the Applications > Sound & Video menu.
(Perhaps a restart of Nautilus would have done it too?)

Install the "-extra" versions of the FFmpeg libs:
libavcodec-extra-52
libavdevice-extra-52
libavformat-extra-52
libavutil-extra-50

Next, in the Kdenlive Settings menu, choose Run Config Wizard.