Before installing and configuring, you need to request activation and homologation to Mercado Pago, access: https://www.mercadopago.com.br/developers/pt/solutions/payments/custom-checkout/appliance-requirements/
If you have any questions, please contact the paid market support directly: https://www.mercadopago.com.br/ajuda
01) Access the Control Panel
02) After login click Modules >> Payment >> MercadoPago Transparent
03) Click the INSTALL button, then click CONFIGURE
04) Fill in the fields:
Public Key
Access Token
After clicking on the UPDATE button