Function PlayerTextDrawShow show a player-textdraw to the player it was created for.
Function PlayerTextDrawShow was added in 0.3e and will not work in earlier versions!
The player-textdraw is only valid for the player it is created for. This means that you can't show a player-textdraw created for a particular player to another player.

(playerid, PlayerText:text)
int playerid The ID of the player to show the textdraw for.
int text The ID of the textdraw to show.

Return Values:
This function does not return any specific values.

// This variable is used to store the id of the textdraw
// so that we can use it throught the script
new PlayerText:welcomeText[MAX_PLAYERS];
public OnPlayerConnect(playerid)
    // First, create the textdraw
    welcomeText[playerid] = CreatePlayerTextDraw(playerid, 320.0, 240.0, "Welcome to my SA-MP server");
    // Now show it
    PlayerTextDrawShow(playerid, welcomeText[playerid]);

Related Functions
The following functions may be useful, as they are related to this function in one way or another.