A typical email format for a position you saw online:
Dear Professor Adeniji,
My name is Olumuyiwa Igbalajobi from Efon Alaaye, a recent of graduate of microbiology, Efon Alaaye University. I came across the advert for the position of XXX in your group at XXX.

My undergrad thesis focused on XX.
Insert your experience....
I am excited by the opportunity to join you group. Particularly, your recent publication on XXX spurred my interest in XXX.
I will appreciate an opportunity to discuss the position and my qualifications with you!

Please find attached my CV and transcripts.
Sincerely,
Olumuyiwa