I'll help, but summoning in 3.X is kind of a pain and might not be worth it long term.
Here are the steps:
1) You cast Summon Monster (x). X is the level of the spell. Now remember that summon monster has a 1
round casting time not 1
action. So you can't do anything else for that turn!
2) If you don't get hit/distracted/dead in that round, your spell goes off next turn at the start of your turn. For this example, let's cast a Summon Monster 1.
a great resource for you is the SRD online. It is your friend! Here is Summon Monster 1
http://www.d20srd.org/srd/spells/summonMonsterI.htm
3) When the spell goes off, you choose a creature from the list provided by the spell. You don't get
anything that is CR 1, just something off the list. Some things have Fiendish or Celestial template. That just adds a few abilities based on how many HD the creature has. HD is listed under the creatures entries. Also, your spell counts as a spell type (good, evil, etc) based on the type of creature you summoned.
Celestial dog is makes the spell good, while
Fiendish dire rat makes the spell evil.
4)Now you have this extra creature, so you basically get to have two turns on your turn, even on your first turn the new creature is around!. When you have a turn, you get your actions (move, standard, etc) and so does your new friend.
Why Summoning kind of sucks- This is an aside. Summoning kind of doesn't get you what you want-a super powerful friend to kill all the bad guys. The creatures you summon are usually a few levels behind you, and will not hit that hard compared to you. Its a good way to throw some hit points between you/your friends and the monsters your righting, but most monsters at your CR will carve up your summoned creatures pretty easily.
In either case, GOOD LUCK BUD!