how do i socialize?

how do i talk to people?i've been quiet for 6 years especially in school,i just sit alone and always zoning out.I don't have any friends,my old best friend is in another school.I 'm in highschool now i should be enjoying my life as a student with my classmates but,here i am being the most quiet and watching them having a circle of friends...whenever i try to get along with my classmates i was led by nervousness and sometimes i overthink the situation.My mother even told me i should make some friends don't just sit and stare"go and get along with them'' does she even know how hard it is to do for me,i mean i've been trying to boost my confidence but it don't always work.I always get jealous whenever i see them being happy and laughing together,just like what happened earlier it was our christmas party some of my classmates are enjoying it while i'm sitting there just staring.