I hav a presario compaq laptop & it wont connect to wifi, my bro laptop connects fine but mines wont plz help?

okay so basically i cant get my laptop to connect to the wifi we have at home dont really no much about computers but i kno enough... it keep sayin that there aint no network to connect to but my bro computer connects fine... at first my laptop was the main line to connect to the wall now we got a desktop and im tired of sittin by the cord... so if u can help i really appreciate it... i dont kno what else to do... also i never tried it until now and i cant call and get help from the company cuz my warranty is nomore... its driving me crazy i want to go in my room with my laptop but i cant get to work...lol.... help plz...