its ok, ive been there too :)
to use a pickaxe, shovel, axe, or any weapon (also a sword) use the button you have labeled "attack" in controls, and if you want to place down blocks, use the button you have labeled "use item". this also works on shears if you want to get wool from sheep. (edit: ususally it starts out in controls as the left mouse button, but you can change all the stuff in controls )
a shelter is just basically a building you can make anyway you want, to protect you from mobs (if you are playing in survival on easy. medium, or hard, peaceful there are no mobs. oh yea, mobs are those monsters that will spawn at night or in dark places, so make sure your house is lit up). you can pretty much make it outta anything you want. make sure you also have a door for it! (to make a crafting table, go to your survival inventory and put four wood planks in the box. to get wood planks, just set the wood you get from trees in the box and itll give you four. in the crafting table just make a shape of a door with wood planks (2 wide, 3 tall) ).
It also helps if you have an iPod touch, or a mobile device you can get apps on, and to get a minecraft guide. most are free, and they give you all the crafting recipes, and helpful tips on mobs and other things.
I hope this helped! i know how difficult and frusturating it can be when nobody has any guides online for starters that are super detailed >_>
Minecraft is an amazing game, and i also hope you have fun playing :D