Howe can i download stuff from internet?

Look at http://www.psychocats.net/ubuntu/installingsoftware

You can download the .deb files to a location on your hard drive, then either double click to prompt the package manager for installation of use dpkg, such as "sudo dpkg -i /path/to/file.deb"

We always recommend the use of the package manager and official repos because it satisfies dependencies and installs trusted packages. If the location of the files is a repo server then you can just add it to your list to simplify updates. If it is just a site with deb files then I recommend caution because the installations are run with root rights and malicious code can cause real damage.