I’m not sure exactly how do you want this to be done . Do you want to leave nullsec in the process or increase it there ?
If you want to leave nullsec , then do what Xeux told you.
If you want to increase your security status there , it can be done via belt ratting and doing the easiest combat anomalies there , like ports iirc. For that you will need at least a cruiser , like a Vexor or Arbitrator fitted with an 100mn AB for speed tanking . You can ask more about this in your corp/alliance , someone will help you, they have these newbie friendly fits and guides on how to use them.
There’s also the Clone Soldier Tags that can help you , if you can afford them.
If you leave nullsec , you can increase it in highsec doing missions or just doing some belt ratting in some relatively empty lowsec systems using a t1 destroyer , just don’t pick 0.1 - 0.2 systems as the rats there are pretty strong for a new player destroyer.
It appears that your security status is currently -2.6 , so when in highsec be careful in 1.0 and 0.9 systems , as there the faction police can attack you . If you go below -5.0 you’ll become an outlaw, any player will be able to attack you in highsec without Concord responding + the faction police.