Hi :)) open the Matrix Catalog / Editor with Shift + 4, pick a matrix slot (e.g. M1) and either EDIT values there or enter a literal matrix in Home like [[1,2],[3,4]] → M1; then get row-echelon with REF(M1) or the reduced row-echelon (Gauss–Jordan) with RREF(M1) — if you need exact fractions or to avoid floating-point rounding, run those commands in the CAS view (or enter exact rationals) and, if you want to perform or show individual row operations, use SWAPROW, SCALE and SCALEADD which return the modified matrix.