FEC has a page detailing foreign nationals' rights in this regard.
It's not long. And it aims at informing the general public (so no specific prior legal knowledge is required). Although, for the interested, it does have the relevant legal references.
For example, despite some of the commentcomments, a foreign national may not "direct, dictate, control, or directly or indirectly participate in the decision-making process with regard to any election-related activities. Such activities include, the making of contributions, donations...