To install libjpeg62
whilst offline, you'll need to download the .deb files for all its dependencies (see Ubuntu Packages) that you don't already have installed as well as the package itself. You would also need all the sub-dependencies, so doing this by hand can quickly become tedious. If you go down that route, once you've downloaded all the .deb files and copied them onto your unconnected computer, install them by running the following in a terminal:
dpkg --install <filename1> <filename2> <etc...>
If you have no way of getting this computer connected to the Internet, though, you might want to look at the answers to this question if you are going to need to install anything else in future: How can I install software or packages without Internet (offline)?
libjpeg62
in the search box, select the package when it appears below, and the Install button should appear to the right. – David Edwards Sep 19 '13 at 10:26