yo - I
tú - you
él - he
ella - she
Usted - you formal
nosotros - we (males and females or just males)
nosotras - we (just females in the group
vosotros - y'all
vosotras - y'all (same ending rules apply like nosotros)
ellos - they (males and females or just males)
ellas - they (all women in the group)
Ustedes - you (plural)
In verb endings, just think of who's in the group.
In the I group - yo. Simple
In the you group - tú. Simple
In the 3rd person - él, ella, usted (usted goes here because its formal and it shows a sign of respect by being in third person)
In the we group - nosotros, nosotras
In the y'all group - vosotros, vosotras
In the they group - Ustedes, ellas, ellos
The way I remember when to use what conjugation is by thinking who it really is. "My dog is tired. " dog - singular, 3rd person, "Mi perro está cansado."
I hope I helped.