How to pick up an object using left mouse button

Sorry, but your question is too broad, and this is not the place to ask for scripts. Unity Answers and its community is here to help you solve any Unity-related problems you have, not give away free code. If you don't know how to write code, I suggest learning Unity's Java Script (its really easy), but if you don't have time, or whatever, then you can try asking your question on the Unity Forums. I hope you can get an answer!

Also, use google. Do tutorials, and learn how to use Unity.

Here are some links I strongly suggest to all new users :

Start at the bottom and work up : http://www.unity3dstudent.com/category/modules/essential-skills/

Start at the bottom and work up : http://www.unity3dstudent.com/category/modules/beginner/

this is the YouTube link for the above as one playlist : http://www.youtube.com/watch?v=-oXYHNSmTxg&list=PL27B696FB515608D2&feature=plcp

Character controller and terrain : http://cgcookie.com/unity/2011/12/05/introduction-to-character-controllers/

That is good to get started. Then start with a small tutorial, this is a simple 2D space shooter : http://www.unityjumpstart.com/ProofOfConcept_1/ : click on the videos part1.mp4 part2,3,4 =]

I just found another by our own Eric : http://wiki.unity3d.com/index.php?title=2DShooter : http://forum.unity3d.com/threads/7883-2D-shooter-tutorial

By then you should be getting the hang of things and starting to have ideas of your own. When you decide what kind of game you want to make, then look at each part you'll need. For example, if you want to make some terrain then walk around it with a character : http://cgcookie.com/unity/2011/12/05/introduction-to-character-controllers/

Here's another on the same 'site but I havn't checked the difficulty : http://cgcookie.com/unity/2012/02/24/game-planning-lunar-lander-01/

Basically then just search for tutorials, there are many out there, either written or on youtube.

the Unity Wiki tutorials : http://wiki.unity3d.com/index.php/Tutorials

A big list of tutorials : http://answers.unity3d.com/questions/12321/how-can-i-start-learning-unity-fast-list-of-tutori.html

Helpful page with information on using Built-In Arrays and Lists (you'll need this later!) : http://www.unifycommunity.com/wiki/index.php?title=Which_Kind_Of_Array_Or_Collection_Should_I_Use?

The unity wiki link above is very handy with lots of scripts and shaders too (just check out all the links down the left, and the tabs along the top : http://wiki.unity3d.com/index.php/Scripts )

http://answers.unity3d.com/questions/148211/list-of-frequently-asked-beginners-questions.html

http://forum.unity3d.com/threads/132628-How-to-help-the-Absolute-Beginner

If you know what kind of game you want to make, edit your question and write there what you are thinking of, then there may be a tutorial out there for that!

But just be aware, you will do lots of typing, deleting, typing, bashing head on desk, being really happy when it works and you understand how and why. I hope this helps, Happy Coding =]