How do I get passed security pattern screen ( forgot pattern)

Try to do a factory reset and let me know if it helps.

Have the tablet powered off first and make sure you have more than 50% charge on the battery. Boot into recovery mode by pressing and holding the volume up and power buttons. At the RCA logo screen, let go of the volume up button and you should next see an android image. Press and hold the power button and tap the volume up button once more and you will be brought to the recovery mode menu. From here, you will need to use your volume up and down buttons to scroll and navigate to the wipe data/factory reset option and use the power button to confirm. When the process is done, go ahead and reboot and your tablet will be set to factory original settings.