when do i use "E" instead of "y"
when do i use "E" instead of "y" when i want to say "and"

Question

Answer

Always for "and" you use in Spanish "y". 
Except when a word begins with "i", then, to avoid a cacophony, you use "e".

For example: 
Mi madre y mi padre fueron al cine ayer. 
María e Isabel vinieron también.

Do you understand? My english is very badly, sorry.

Answer

When next word start with "i" or "hi". But never when start with "hie.." (because "hie..." sounds ot as vowel = aprox. like "ye"

aguja e hilo
But:  agua y hielo