Try this:

    // SPDX-License-Identifier: MIT
    pragma solidity >=0.4.22 <0.9.0;

    contract Jar
    {
      uint[][] m = [[4, 6], [5, 7]];

      function fillMultidimensionalArray(uint _firstValue, uint _secondValue) public {
        // You must declare the array which will be inserted into the multidimensional array
        uint[] memory v = new uint[](2);
        // Then after initializing, you must populate the array
        v[0] = _firstValue;
        v[1] = _secondValue;
        // And here, you put the array 'v' into 'm' (multidimensional array)
        m.push(v);
      }

      function getV(uint _firstIndex, uint _secondIndex) public view returns (uint)
      {
        return m[_firstIndex][_secondIndex];
      }

    }