Question about searching through strings.

[xsoifonx]

Hello I'm stuck on an assignment where I have to open an fin file and then search each line for an "@" sign. When I find an @ sign I'm supposed to take that and make it one line. If there's more than one @ sign it should be two lines. How do I do this? I have no idea how to even begin this program. Thank you so much for helping me out.