First you need to download the official firmware from the link below.
Too install new R4 firmware.
Step 1. Place the files below directly into your microSD
Step 2. Unplug your MicroSD USB and place your microSD into your R4 cartridge then turn it on you should now see the R4 menu.
Step 3. Then drag-and-drop, copy and paste your games anywhere inside the microSD card.
Hope this helps!