Once you have downloaded the installer, start it by typing (replace X_Y_Z below by the version number of LoadUI)
Click Next to specify the path to the installation folder
Here you can change the install folder, if you need to, and then click on Next
Here, you can change the folder for symlinks, if you wish. Click Next, the installation will start
At this point, the installation is completed, read the information on the page and click on Finish to close the dialog.