Certainly symbolism is a key element of all of Frost's poetry. In particular, you might like to think about how he uses the natural world as key symbols in his poems to suggest much bigger and deeper ideas about death, choices and success.
For example in "Stopping by Woods on a Snowy Evening," the woods are described as being "lovely, dark and deep." They are clearly an attractive place, and although tempted to stay and delight in their quietness and beauty, the speaker "has promises to keep." Thus we could argue that symbolically the woods represent death that the speaker does not feel able to take up because of the responsibilities that he has.
Likewise, in "After Apple-Picking," the world of work and labour is represented in the harvest of the apple-picking. Note what the speaker says about this work:
For I have had too much
Of apple-picking: I am overtired
Of the great harvest I myself desired.
Success, as defined in the quantity of apples, has exhausted the speaker, and thus this poem symbolically comments on work and success.
However, perhaps in his most famous poem, the haunting necessity of taking decisions is summarised in "The Road not Taken," where the speaker is forced to make a decision between two paths that would lead him to different destinations. These paths and the choice of course symbolise the decisions that we all have to make in life but which we are never able to undo or go back and select another "path."
Thus through looking at these three examples of Frost's work, we can see how his poetry operates through natural symbolism to comment upon realities such as life, death, labour, success and decisions.