Step 1: Put $n = 1$ to get the first term.
$$a_1 = 3(1) - 2 = 1$$
Step 2: Put $n = 28$ to get the $28^{th}$ term.
$$a_{28} = 3(28) - 2 = 84 - 2 = 82$$
Step 3: Use $$S_n = \frac{n}{2}(a_1 + a_n)$$
Step 4: $$S_{28} = \frac{28}{2}(1 + 82) = 14 \times 83 = 1162$$
Hence the sum of the first $28$ terms $= 1162$.