THE PEOPLE of this country made it very plain that they approved what we've been doing and we're going to continue what we've been doing." That's how President Reagan interprets his electoral landslide. Hardly anyone would disagree. But what does that general approval imply for policy?

What, to take the subject that concerned so many voters, are the implications for his economic policies? The problem with finding the answer is that, apart from reaffirming his commitment to budget discipline and his unswerving antipathy to taxes, the president was calculatedly vague about his budget plans during the campaign. Even his first-term policies -- the "what we've been doing" that the voters presumably endorsed -- offer scant guidance.

Remember that after the big domestic budget cuts of his first year, the president essentially ceded full responsibility for tax and budget plans to Congress. Congress did take back some of the excessive 1981 tax cuts and it put additional restraints on social programs. But because of big growth in military and other programs, total spending continued to grow. And, of course, with revenues lagging, the deficit grew still faster. This cannot be what voters want.

Over the next two months the president will have to decide whether more forceful action is needed. No doubt the budget he unveils in January will attempt to minimize the apparent need for action on the deficit by assuming high continued growth and dropping interest rates together with the usual vague claims for "management savings." But the president's budget advisers will almost surely press him to sign off on concrete budget cuts that promise a more plausible narrowing of the deficit -- at least until five years hence when someone else will be in charge.

The easy budget pickings are gone. But, even with Social Secuity and defense off limits, substantial future savings could still be amassed by revamping farm subsidies and federal pensions, curbing veterans' health services and public works projects, and putting new limits on Medicare. None of these savings amounts to much by itself. All will be stoutly, and in some cases correctly, resisted by powerful lobbies. With a divided and disgruntled Congress, the president would have to prepare for a hard personal battle. These budget choices will be the first real indication of what the president thinks his victory means.