How to vocally sight read?

well idont know how well you’ll do if you have to learn solfedge in two days but ill try to basically explain it. solfedge is the Do Re Mi Fa So La Ti Do you just sing the pitch of the note to do re mi (etc.) instead of words so on a staff, which is where the notes are on a sheet of music (idunno how much you know about it) but each note on the staff represents either Do, Re, Mi, Fa, So, La, Ti, or Do again. and when you sight read when you come to the note instead of singing words, you’ll sing the Solfedge. now to figure out which note is which, whichever key youre singing in lets say its C. well, the C on the staff will be Do. then D will be Re, E will be Mi so on and so forth. thats going up the scale. if youre going down in the key of C then C is still Do, and B is Ti, like going down the Do Re Mi Fa So La Ti Do. and that means A would be La so on and so on. if you dont know how to read notes on a sheet of music an easy way to learn is to think of Every Good Boy Does Fine

and

F A C E

that helps because on the staff the notes in the spaces going from the bottom up are are F, A, C and then E. thats were you get face. and the notes on the line of the staff going bottom up are E, G, B, D, F. every good boy does fine.

so lets say you start in the key of F, then every F would be Do, and if youre singing G then G would be Do so on and so forth. I hope I did okay explaining it if you have any questions you can message me