FlowChart.NET does not provide automatic data binding, so you will have to create ADO.NET datasets from your process and relation tables; then enumerate the records in the datasets and create a Box instance for each process and Arrow instance for each relation.

Do you already have a database schema describing the processes and relations or it's yet to be designed ?

In the general case there would be a many-to-many relationship between the processes, which you could present using an auxiliary table. E.g. if the main table is

Process
----------------
id : integer
title: text
details: text

then implement the relations as

ProcessRelations
----------------
successorId : foreign key to [Process]Id
predecessorId : foreign key to [Process]Id

It should be easy to map that schema to a FlowChart.NET diagram. At the end you would have to arrange the nodes and links, by either setting directly the BoundingRect and ControlPoints properties or using one of the automatic layout routines provided.