It is important to note that LEDs are primarily current driven devices - that is, the current, and especially the maximum current, is what you need to control. This should be well documented in the specification (or data) sheet for the specific parts you have.
For high output LEDs, thermal management is also important, and will also be discussed in the data sheet and possibly also in application notes.
As such, a sophisticated approach to LED operation is to build a current source. The typical voltage source + resistor is a crude and often perfectly adequate approximation - but you need to design those pessimistically or you may find that the LEDs expire somewhat before you anticipated it. So, if you are running 7 LEDs in parallel which have an operating voltage range of 3.0-3.6 volts, you design as if they were 3.0 (or 2.9) volts when operating and select a resistor (one for each LED) that will pass the appropriate current (maximum or somewhat less) based on that assumption. So if you have a 20 mA LED and a 5 V supply, you subtract 3V from 5V to get 2V across the resistor, and 100 ohms comes out for the resistor.
If your supply is 12V you either get 450 ohms, or you stack a couple LEDs in series and use 300 ohms, or 3 in series and use 150 ohms.
It's always safe and usually advisable to use a bit more resistance (less current) - LEDs die quickly when the current is too high, and live a long time when it is low. If your LEDs have a different current rating, just apply
R=V/Ito determine the correct resistor size.
Or, look into simple current sources (such as the ever popular LM317 adjustable voltage regulator in current source mode) and drive your LEDs with a current source.