I want to install realplayer in Ubuntu. But I dont have internet connection at home to under go repositories. How to proceed?

Helix-player is Real's open-source version of Realplayer.
You can download the package you need to install helix-player from packages.ubuntu.com , transfer that to your home computer, and install it there.
the specific link is here . this is for ubuntu 7.10 (gutsy) , you can find packages for other versions of ubuntu there too.
http://packages.ubuntu.com/gutsy/graphics/helix-player
you probably want to download the package labelled i386 , unless you use a mac or 64-bit pc.

on that page there is a list of packages upon which helix-player depends, it would be wise to check whether your home computer has those, and if necessary download them too.

a more sustainable solution would be download onto the disc all the packages that aren't on the ubuntu install cd. these are in two repositories called universe and multiverse.

you can read about repositories here https://help.ubuntu.com/community/Repositories/Ubuntu
if you search you might be able to find a dvd image to download with the universe and multiverse on

alternatively, you could try download realplayer from http://uk.real.com/player/more

The correct page for realplayer for linux is http://www.real.com/linux/