You need to use the \ character i.e a backslash. From the bash man page:
A non-quoted backslash '\' is the Bash escape character. It preserves the literal value of the next character that follows, with the exception of newline. If a \newline pair appears, and the backslash itself is not quoted, the \newline is treated as a line continuation (that is, it is removed from the input stream and effectively ignored).
commannd1 arg1 arg2 \
commannd1 -arg1 -arg2 \
-arg3 -arg4 \
The following command is used to compile and install nginx web server. A backslash (\) is used as to continue command on the next line:
./configure --without-http_autoindex_module --without-http_ssi_module \ --without-http_userid_module --without-http_auth_basic_module \ --without-http_geo_module --without-http_fastcgi_module \ --without-http_empty_gif_module --with-openssl=/lib64