How do I use a Trie for spell checking

I think you should instead give a try to bk-trees; it's a data structure that fits well spell-checking as it will allow you to compute efficiently the edit distance with the words of your dictionary.

This link gives a good insight into BK-trees applied to spell-checking

Try computing for each tree node an array A where A[x] the smallest edit distance to be at that position in the trie after matching the first x letters of the target word.

You can then stop examining any nodes if every element in the array is greater than your target distance.

For example, with a trie containing MAN and MANE and an input BANE:

Node 0 representing '', A=[0,1,2,3,4]
Node 1 representing 'M', A=[1,1,2,3,4]
Node 2 representing 'MA', A=[2,1,1,2,3]
Node 3 representing 'MAN' A=[3,2,2,1,2]
Node 4 representing 'MANE' A=[4,3,2,2,1]

The smallest value for A[end] is 1 reached with the word 'MANE' so this is the best match.