Hello, Steven Tay,
Thank you for contacting us and for using XStore.
You may use additional plugins, however, please note that providing support or making changes to them is not included in our basic support scope.
Please try adding the following code to the Theme Options > Theme Custom CSS > Mobile section:
.woocommerce-checkout .payment_methods {
text-align: center;
}
.woocommerce-checkout .ppcp-button-container {
min-width: unset;
}
.woocommerce-checkout .payment_box {
padding-left: 0px;
}
Kind Regards,
8theme team