As mentioned above, the basic principle is simple. You have a project with subprojects, tasks, milestones, etcetera. You have specified the order in which the tasks must be executed. The tasks are then scheduled consecutively, and they always start as soon as possible:
After the first activity has completed, activities 2 and 3 will start at the same time. Activity 4 will not start until the longest running activity of these two activities has finished. After the end of this activity, the first milestone arrives. Once the first subproject has been completed, the second subproject starts.
The subprojects follow their contents: the start date of the first activity determines the start date of the subproject, and the last finish date determines the end of the subproject.
Weekend days are not work days. In the example, you can see that the bar of the third activity continues through the weekend. This weekend time is not deducted from the lead time, however.