Adding CCS, Javascripts and PHP files into Joomla websites -

i quite new joomla , have come across problem annoys me programmer alot!

now ive been watching several tutorials on-line , of them state "its easy non programmers create website joomla"

while that's fine , there seem few tutorials show "powers" have if infact have programmering experience.

here problem:

i want able add php, javascripts css , html site have stumbled across jumi far know allows me add scripts articles , modules.

here example of want achieve:

i buy , use template @ themeforest want create search bar using html , php, when using search option site run script , load result table using combination of jquery , html.

other wish create session when user example tries purches items on site saved , site remembers users choices.

now not except guys have answers simple redirect tutorial, paper or other place can learn how make work make me gratefull.

question update

so think question abit hard understand ive made update:

maybe have misunderstood things instance 1 of guys download template how go on there? how manipulate modules when search search done in database table default one? how create login users use , add own costum scripts?

these few examples hope idea.

read more abou joomla modules. allow add bits of own custom functionality websites :

http://docs.joomla.org/module

[update]

if need create more self-contained bits of functionalites operate on own db tables ect need build component (the tutorial below quite hands-on):

http://docs.joomla.org/j2.5:developing_a_mvc_component/developing_a_basic_component

i realize joomla docs not great. myself learned studying code of core templates , components