here's a website where you can import data from 1 minute, or one day.
http://www.alpari-idc.com/en/dc/databank.php
once you have downloaded the desired currency pair, (don't worry that they don't have 15 minutes, i'll explain that later) here is how to import history:
while in the metatrader 4 platform, click "F2", (or click "tools", then "history center")
go to where it says import, (at the bottom), a window will pop up. in the top-right corner, there is a button called "browse" click this button, and find the file you downloaded from the above site.
once you've found it, click open, (the window should dissappear), in the window now titled, "Import..." there should be candlestics that appear in the box below. after all this is done, push "ok" at the bottom.
near the middle, at the top of the history center, it will say, "Database_______ records" the number in the blank should rise to or above 100,000 records. once you have made sure of this, close the history center.
converting 1 minute data to 15 minute data:
open your currency pair, and set it to 1 minute data. open the navigator, (if it's not there push "Ctrl" and then push "n".
there will be a tab called "scripts", open this tab and look for period seperator, (i think it's a standard script that comes with the metatrader4 package, but i'm not sure, just in case, i have attached the file, save this file under the the "experts" folder under "scripts" the script should then appear under this menu)
click and drag where it says "period seperator" onto the chart, it'll bring up a box. it should standardly pop up the "inputs" tab at the top. it will say "Ext PeriodMultiplier" under value, type "15".
simple as that
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