Blinking of LED's in OpenCL

I would highly advice against beginners using OpenCL on FPGAs to try to create designs that involve manual pin configuration.

By standard, the manufacturer provides a Board Support Package (BSP) with all the IP Cores that access FPGA pins already implemented and configured. OpenCL does NOT provide a direct way to get access to the FPGA pins, except through the BSP. To access the FPGA pins that do not have an existing interface in the BSP, you have to create one yourself and recreate the BSP. Doing so requires modifying the BSP and adding your interface based on the standard interface that OpenCL requires, and creating an I/O channel that can be accessed in an OpenCL kernel. Then you can use that I/O channel from the kernel to drive the pins to, for example, turn on some LEDs. This requires extensive knowledge of hardware programming, Quartus/QSYS, the OpenCL interface used by Altera, and timing closure. You can find the official document that details creating a custom BSP, here (https://www.altera.com/en_us/pdfs/literature/hb/opencl-sdk/ug_aocl_custom_platform_toolkit.pdf).

Please note that at the end of the day, achieving this particular goal using Verilog/VHDL will be far much faster and easier compared to OpenCL.