URL    = "https://b24-ar17wx.bitrix24.by/rest/1/ztbe...";
    ChatID = "454";

    UserIDs = New Array;
    UserIDs.Add(10);
    UserIDs.Add(12);

    Result = OPI_Bitrix24.AddUsersToChat(URL, ChatID, UserIDs);

    URL    = "b24-ar17wx.bitrix24.by";
    Token  = "c03fa966006e9f06006b12e400000001000...";
    ChatID = "456";
    UserID = 10;

    Result = OPI_Bitrix24.AddUsersToChat(URL, ChatID, UserID, True, Token);