Yu-Gi-Oh! cards are my favorite, but I never been in a tournament. I was wondering can anyone tell me if I can summon a lvl. 1-4 monster from my hand when it’s my first turn?
Yes you can, however in yugioh you will refer to the stars as levels which go from the right hand side of the card, and with XYZ monsters the stars are known as ranks which go from the left of the card.
Further description on summoning:
In yugioh there are what is known as normal summons and special summons. Special summons usually (special summoning from the extra deck doesn't always come from a card effect) occur via card effects and usually state what kind of monster that effect can special summon for example the card ancient rules
Special Summon 1 Level 5 or higher Normal Monster from your hand.
This effect states the type of monster it can summon (being a level 5 or higher normal monster)
You can special summon monsters as many times as you want per turn
For normal summons this is a bit trickier, you can only conduct one normal summon per turn unless you have a card that allows you to make more normal summons like double summon
You can conduct 2 Normal Summons/Sets this turn, not just 1.
With a normal summon you can summon a level 1-4 monster straight away however you to summon a level 5 or higher monster you must first tribute (send to the graveyard) monster(s) already on your field. Level 5 and 6 monsters require you to tribute one preexisting monster on the field and level 7 or higher monsters require 2 preexisting monsters on the field unless the monster states in its card text otherwise like Obelisk the Tormentor emphasis mine
Requires 3 Tributes to Normal Summon (cannot be Normal Set). This card's Normal Summon cannot be negated. When Normal Summoned, cards and effects cannot be activated. Cannot be targeted by Spells, Traps, or card effects. Once per turn, during the End Phase, if this card was Special Summoned: Send it to the Graveyard. You can Tribute 2 monsters; destroy all monsters your opponent controls. This card cannot declare an attack the turn this effect is activated.
These are what is known as a tribute summon. Tribute summons are a type of normal summon so they do count as your one normal summon for the turn.
You can find more information about summoning in the rule book on page 18.
I was wondering can anyone tell me if I can summon a 1-4 star monster from my hand when it’s my first turn?
The real answer is it depends. Depends on the specific monster, and also if you have additional cards or effects that may state otherwise.
Still, in a few words: unless such monster indicates otherwise, there is nothing restricting you to Normal Summon a 1-4 starred monster. From the rulebook, page 20, on Normal Summoning, emphasis mine:
This is the most common way to Summon a monster. Simply play a Monster Card from your hand onto the field in face-up Attack Position. All Normal Monsters, and most Effect monsters (unless they have a specific restriction), can be Summoned in this way.
However [...] Monsters that are Level 5 or 6 require 1 Tribute and Monsters that are Level 7 or higher require 2 Tributes.
As you can see any lvl 1-4 monster can be summoned that way unless it has a specific restriction. You can also set lvl 1-4 monsters directly from your hand, even though that is not considered a Summon (which is what you asked). From the rulebook again:
To play a Monster Card from your hand in face-down Defense Position is called a Set. In order to Set monsters that are Level 5 or higher, you still need to Tribute. It is important to remember that a monster Set on the field in face-down Defense Position IS NOT considered Summoned.
Finally, I also suggest you consult with your tournament judge, so they can provide you with a more in-depth rule explanation and also bring you up-to-speed with the specific rulings and context of that tournament.