How do I control the text size of my email page?

When I go to yahoo home page using Firefox and click the email icon, the normal page appears with all the information but the text is so small it is unreadable. Because I cannot read my yahoo email I would appreciate receiving any help at my Juno address: nles@juno.com. Thank you njl.How do I control the text size of my email page?
When the text (etc) appears too small-----press and hold down the ';ctrl'; key while rolling the mouse wheel backwards and forwards to adjust it to suit yourself.How do I control the text size of my email page?
In Yahoo Mail, look at top right where it says ';Page'; with down arrow. Click on down arrow and you will see ';Text Size'; click the right arrow and you will see options for small, medium and largest font. Click on the size you want to try. I am pretty sure this is how you change your font size in Yahoo mail.