I have 3 w-2s but I’m only filling one because the other two I only work at the jobs for one 2 months and 3 months

[DoninGA]

You enter ALL income received in 2019.  You enter ALL 2019 W-2's received on only ONE 2019 tax return. 

[VolvoGirl]

Your tax return is based on your total income for the year.  Not based on time.  The IRS gets copies of all the W2s and will be expecting to see them on your return or they will mail you a letter and probably a bill.

if you didn't enter them all before you filed you need to amend to add them.