If the string of characters is encoded in bytes as ASCII you should be able to break the received string into bytes and send them one by one to the LCD module. Some modules include an alternate font and if you intend to use that then you will have to arrange to map the string bytes to correspond to the font byte encoding in the LCD module. Before the LCD module can accept the bytes it must be properly initialized.

There are numerous examples of LCD code on this site in the Code Library (see button at left) and in several of the User Pages/b> (also see button at left).

Once you get it so that you are seeing the characters show up on the LCD module you will have to devise a way to deal with the fact that you have four lines. Your LCD module will have commands that allow you to change the insertion point as to where the next character will appear and this can be used along with some idea of how long you allow the strings to be. You may also want to devise a means to send the row and column number along with the data received at the UART that would specify place a string will start on the display.

Good Luck.
Michael Karas