Hi, and welcome!
Not needed for this question, but for future reference, please see FAQ: What's a reproducible example (`reprex`) and how do I do one?
read.csv recognizes the first line as the header by default. I suggest opening the csv file and confirming that there are no blank lines. Alternatively, if the data is otherwise ok, you can add the headers with
colnames(YOUR_DF) <- c("fee","fi","foo","fum")