Begin each line of dialogue with a double quotation mark for American English or a single quotation mark if writing in British English. Note that the use of American or British English does not indicate what the character is speaking, but what you, the writer, are using.
Write the words the character is speaking after the quotation marks.
Place a period and close the dialogue with another quotation mark when the character is finished speaking.
To identify the speaker, add a comma at the end of a line of dialogue instead of a period, then the quotation mark followed by the words "she said," "he said" or something similar that lets the reader know which character was speaking.