I will need a power supply bigger than the Forward Voltage of 6 V right?
so if i keep my voltage around 7 to 8 V it will be good. will it be better with 12 V?
if i use a second led in series my power supply has to be bigger than 12 V right because the voltage drop acrross each led will be 6V so 6 times 2 is 12 V..?
Most high power LEDs are first reflow soldered to a mcpcb ( metal core printed circuit board ). That mcpcb while itself being a form of a heat sink, is usually too small to dissipate the heat of a 700mA LED. Thus, that mcpcb with the LED then is mounted to a bigger heat sink either with thermal epoxy, thermal tape or thermal paste and screws.
Reflow soldering this LED " in the raw" to an mcpcb takes some form of equipment that most beginners don't have on hand, or experience with.
If you are interested in that specific LED, perhaps look for a supplier that has this mounted already on a mcpcb.