Process might vary by Presbyterian denomination. In the PCA you should make reference to the Rules of Discipline (starting at Chapter 27 in the Book of Church Order.) But generally, only a charge against a preacher would be initiated at Presbytery. Charges against members would be initiated at the session. BCO Chapter 31 and 33. There are provisions where the Session refuses to act, in the case of a member, or the Presbytery in the case of a preacher, and a higher court can assume jurisdiction, but the process for doing so is more difficult. In short, if one goes after the pastor he or she can go directly to the presbytery; if the complaint is against the entire session, you either petition them to correct their error. (and appeal an adverse ruling) or you need to enlist the support of the sessions of two other churches. As Dr. Duguid suggests, get someone who knows what they are doing to help.
But, really, if the complaint is with regard to an action of the session, a well presented argument should be made to them with an opportunity for them to correct themselves. Or, even before that, meet with one or two members of the session to hear their position on the issue and find out where the members of the session stand.