14.04 - Blender 2.70 not installed, but can open it, yet can't find it in dash or add it to launcher

I have downloaded Blender 2.7 and moved it to folder /opt and yet I can't find it in dash or place it in launcher. I have searched for solutions on the net, but I don't quite understand those.

Unless you absolutely need features or bug fixes only present in Blender 2.70 I'd use the version available in the Ubuntu repositories (2.69 for 14.04).

You can easily install it from the Terminal (Ctrl+Alt+t):

sudo apt-get install blender

Properly packaged for Ubuntu, Blender comes with a .desktop file (see the package list) allowing the dash to find it (and can also be used as a launcher icon).

UPDATE:

I assume that you installed blender in /opt/blender-2.70a-linux-glibc211-x86_64.

So the only thing missing to enable dash search and a launcher icon is a .desktop file like this one:

[Desktop Entry]
Version=2.70a
Name=Blender
GenericName=3D modeller
GenericName[es]=modelador 3D
GenericName[de]=3D-Modellierer
GenericName[fr]=modeleur 3D
GenericName[ru]=Редактор 3D-моделей
Comment=3D modeling, animation, rendering and post-production
Comment[es]=modelado 3D, animación, renderizado y post-producción
Comment[de]=3D-Modellierung, Animation, Rendering und Nachbearbeitung
Exec=/opt/blender-2.70a-linux-glibc211-x86_64/blender
Icon=/opt/blender-2.70a-linux-glibc211-x86_64/icons/256x256/apps/blender.png
Terminal=false
Type=Application
Categories=Graphics;3DGraphics;
MimeType=application/x-blender;

After you've created this blender.desktop file, just drag and drop it somewhere onto your launcher.

Note: You may have to change the path to the blender exe/icon if you downloaded the i386 tar.bz2.