If you type a statement that is too long to fit on one line, the editor will "wrap" the statement in order to allow it to continue onto additional lines. In other words, just keep typing and the editor will automatically continue the statement onto as many lines as needed.
There is an alternative way of dealing with long statements that gives you more control over the formatting of a statement that extends across multiple lines. A line that begins with a space or tab character is treated as a continuation of the preceding line. To continue a statement on an additional line, press the ENTER key and then type a space or tab character at the beginning of the next line. For example, the statement
y = x1 + x2 + x3 + (1) error
can be written using four lines as follows:
y = x1
+ x2
+ x3
+ (1) error
where lines 2, 3 and 4 each begin with a space and are therefore treated as continuations of the statement that begins in line 1.