I am glad to hear that you got past your original problem.
As for your second problem of calculating travel time polygons for pedestrian travel times, your attachment appears to be invalid (i.e., I get an error message when I click on it). Please re-try attaching the image(s), and we can discuss this further.
Regarding your last question about what fields must be present for your network dataset, there are several levels of detail you can establish in your data, depending upon your modeling requirements. The most basic requirements would be for you to have some source of travel costs for your edges. This is often represented as either travel distance (e.g., using a length field) or travel time (e.g., derived from length and speed limit fields) or perhaps even both (modeled as separate cost attributes in your network dataset). A cost attribute is required to perform any realistic shortest path analysis on your network.
A next step would be to determine whether or not your data supports any restrictions for modeling real-world travel constraints on your road network (e.g., oneway streets or restricted turns). These can be modeled as restriction attributes in your network dataset. Oneway restrictions are often derived from simple boolean fields in your dataset (to indicate whether or not a street is oneway for a given travel direction). Restricted turns (or even turn delays) can either be modeled globally (i.e., applied universally to all possible two-part turns) or established for only an explicit set of turns in your network (this latter possibility requires you to create a turn source feature class).
Finally, you might also wish to establish support for generating driving directions on your dataset. This requires a street name field, as well as a specification of a length cost attribute and time cost attribute.
Of course, there are several other possibilities you might wish to consider when building your network datasets, but these are the most common. For a more detailed discussion of all of this (and more), including walkthroughs of building network datasets on sample data, I would strongly encourage you to work through the Network Analyst tutorial (this comes with your installation of ArcGIS). This includes examples of everything I have touched on above, as well as some more complex modeling scenarios. This is the best place to get started, and this will help you get a feel for how to setup your own network datasets using your own data.
If you have any further questions, please let me know.