Hello Cetjohn,
Based on the image you included, you would press the Continue button on that prompt and then follow the on screen instructions.
If the prompt keeps coming back after you go through the instructions, try signing out of your Apple ID account on the device and back in.
Go to Settings > name at the top, then scroll down and select Sign Out at the bottom. Once the account is fully signed out, go ahead and sign back into it.
If you're still unable to get through the encryption prompt, you'll want to contact Apple for assistance with your account: Get Support
Cheers!