Ok so as you have guessed use the team builder.
Your team builder should look like this.
In the search box type the pokemon you want then ill go through each aspect.
Picking the nature and evs are easy, drag the bar (While keeping an eye on the evs on the right) Or simply type in the amount wanted.
You can change your nature by using the drop down box or clicking next to the desired stats.
Picking the moves are easy.
If you cant find a move, start typing in the moves name then a drop down box will come up with possible matches.
This is helpfull for pokemon like mew.
You can catagorise the moves as well by clicking on the boxs above (So type will order all moves in type order in alphabetial order typewise)
Choosing your hidden power is also easy but there are many combinations.
Under alternative forms it will show you all compatable iv matches, this is helpfull when you want lets say spatk when you would origionally loose it.
Picking the ivs are also easy they are set at default but can be dited to pick your combination for hp or running trick room abusers.
The abilitys will change its tiers and move choices so make sure your moveset is useable with the desired ability.
Altered form is for pokemon like deoxys, if the pokemon needs an item give it the item needed in the bottom left hand corner.
Happiness determins return and frustration 255 is max happiness.
Once the team is made (make sure all natures are done as are moves otherwise in a battle it becomes missingo) save it.
Give it an appropriate name so for the team above i would name it Rubbish.
You can keep boxes as well to keep sets and teams.
The exportable copy is for when you want to post a team or import to other simulaters.
Import is for importing exportable copys.
Make sure that there are spaces between each pokemon other wise only the lead will show.
Sometimes the natures become hardy when importing.
When saved exit and go online.
Pick the desired server. (smogon p are best for getting quik battles)
Click find battle choose your options for variations, singles, doubles, tripples, same tier.
You can go to file then load team to load saved teams quikly.
You can also open the team builder with ctrl o.
Go to tiers to select tiers you will be set to default but if you have illeagle pokemon like the evnt raikou with adamant nature, not only are you stupid but you will be put in the challenge cup tier.
You can veiw your rank and others in there tier they are currently playing by double clicking them.
This will also possible show you there team(depends how they edited there settings) and lets you challenge random people.
They may also hide there rank, left click then veiw rank.
You get points for winning battles and -points for loosing.
You start at 1000 and a good rank to be at is around 1100 the highest people are usually around 1500-1700 depending on the tier.
You can edit your settings using the toolbar.
This allows you to show or hide your rank and team.
You can change your theme as well.
Finally if a tournement is on you wish to join, type in the chat box /join that will send you to the tournement.