What the speaker is saying in these lines, the first two of the poem, is that he and the young woman he wants to sleep with do not have all the time in the world. She is, evidently, rebuffing his attempts to become physically intimate—presumably in an effort to preserve what he later calls her "quaint honour"—and so he calls her "coy," which means that she is shrinking from this intimate contact with him. He suggests that, if they did have unlimited time, then it would not be a crime, would not be a waste, for her to be coy with him. He implies that, because human life is short and time is fleeting, it is actually a "crime" for her to waste any of the time they could be enjoying together by being coy and standoffish.
The speaker addresses his would-be lover directly in these lines, evidently hoping to convince her not to worry about her "honour" but to consider how little time they really do have together. Now, they are young and beautiful, but youth and beauty fade quickly, and he wants her to take advantage of this time of high passion with him now. The first two lines of the poem help to establish his line of reasoning: that life is short and they should make the most of the time they have together.