Mysql to use all cores 20 cores I have

I am currently setting up a website that uses a mysql database having more than 4 crore rows of data. I am using one server for files and separate mysql server. Two servers are having 20 core, 64 gb ram. Meanwhile I could see while executing longest mysql queries my mysql server is using two cores maximum hence it is taking more than 38 seconds to execute my longest query. see the result below.

User@Host: dev_data @ localhost []

Query_time: 38.113460 Lock_time: 0.000514 Rows_sent: 10 Rows_examined: 48683733

How can i configure my mysql server so that it uses all the 20 cores to handle the mysql ? How can I achieve this ? Mysql version using 5.6

Atop result below.

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