How can I get root-like permissions so I can download stuff from the software center?

Open a terminal by pressing CTRL+ALT+T and enter id This lists the groups you belong to.

If you are using Ubuntu 12.04 or later then look for the group sudo in earlier versions the group was admin. If you are shown as being in this group you are a system administrator and can run commands with administrator privileges. If not then you will need to ask an administrator to either make you an administrator too or do what you want

An administrator can make you one too by running sudo adduser username sudo or sudo adduser username admin as appropriate for the version of Ubuntu you have replacing username with your user name.

If you are already an administrator then to run a program with a GUI with admin privileges press ALT+F2 to open the command line and type gksu or gksudo followed by the name of the program you want to run. For example gksu nautilus runs the filemanager. gksudo is just a link to gksu so both commands are equivalent.

For command line applications then prefix the command with sudo you will be asked to enter your password. There is no feedback when you type but it is being acceped.

For the specific example of installing preload the command is

sudo apt-get install preload

This is explained in more detail in the RootSudo - Community Ubuntu Documentation

Provided you know the package you are looking for, you can use sudo apt-get install x where x is the package you are looking for.

Basically, for your Preload (for example) you would use:

sudo apt-get install preload

sudo temporarily gives you root permissions. You may want to read up on https://help.ubuntu.com/10.04/administrative/C/terminal.html or even better use man sudo.

You can use the man pages to better understand the commands you use, to help you understand where they will help you.

You are completely wrong. You are using a non-administrative account, so you can't install software trough terminal.

The reason is because you don't have a sudo password (yes, sudo, not root).

You can (if not, you have another problem, new question) install software trough the software center with a sudo password of an administrative user.

If you want to have administrative privileges, then you need to add the user in the sudo group.

You have to know the difference between sudo and root. Root is not a command, sudo is not a user..