Does anyone know how to write a sonnet? I need to write a sonnet about Romeo & Juliet to show I understood the play.

Depends on the sonnet

Shakespearen is the easiest, the requirements are:

14 lines

iambic pentameter (10 beats per line)

abab cdcd efef gg rhyme scheme

gg is like a shift from the rest of the poem between lines 13 and 14

has to be about some type of love

petrarchan:

14 lines

two stanzas then the two lines

iambic pentameter

also has specific rhyme scheme

Abba Abba cdecde or cdcdcd shift after the first 8 lines

has to be about some type of love

there is also spencerian and modern but these are more common and the shakespeare one is the easier one honestly