You can get the length of a string with .length() or .size(): string s = "hello"; int len = s.length(); gives you 5, the number of characters. Access individual characters with square brackets: s[0] is h, s[1] is e.
Indices start at 0, so the last character is at index s.length() - 1. Concatenate strings with +: string full = "hello" + " " + "world"; creates "hello world". You can also append to an existing string with the += operator.