The best way to start, if you have the information, is with the Spouses. This will give you a lead as to where to look for entries of the Stewart husband or wife. I hope that this index may be useful to non-Stewart visitors as well; there are a great many surnames in there!
But if you are really lost in space, the best way might be to check the Places. This index includes all references to towns and counties in the US, as well as names of tracts if given, and of course counties, states and countries that were mentioned in general, when more specific information was not known. I have also included the entries for counties and states all the times a little history was thrown in, because in the early days the boundaries, especially in the South, changed radically and often.
But if you know who you are looking for (happy you!), check the Index of Stewarts - alphabetical. There is also a small index of Stewarts without first names. And there is the other Index of Stewarts - by family -- the same list, sorted by parents. This is especially useful if you know of two or three children that were all from the same family, or if you want to check on the whole family of your Stewart.