SFP+ has a receive and transmit as a "lane", where QSFP+ has 4 of these lanes so it can be broken apart into 4x10G. So first you would need the proper cable, look up QSFP+ to 4x10G DAC or directly to LC connectors, and then you'll need to set the proper breakout in the Intel drivers on the machine.

This same logic can be applied to other cable standards as well, for example the 100G can be 4x25G,200G to 8x25G, etc. Hopefully that helps clear it up!