Submitting Plans to the city/county building department for plan check is how to commence with step four.
The basic minimum design package needs to be collected together for this submittal includes:

Site Plan
Grading Plan (sometimes incorporated into site plan)
Building Plans
Structural Engineering
Geo-technical Soils Report
Title-24 Energy Documentation
Truss Calcs.(if trusses used, sometimes may be deferred)
Erosion Control Plan (sometimes incorporated into the site plan)
Fire Sprinkler Plan (somethimes may be deferred)

There may be other design elements that are required depending upon your property and building department,  but these are the basics.

At this point, the plans are to be scrutinized by the planning, building and health authorities at the ‘Community Development Agency.’  This process can take at least a few months to complete.  They red-mark the plans and make a list of incomplete/incorrect items that need to be dealt with prior to issuing a building permit.  Depending upon the municipality, this process can be a breeze or it can be quite frustrating and time consuming.  The government rarely seems to be interested in ‘our’ schedule.  Regardless, it is a necessary step to get the permit.

Once the permit is issued, congratulations!  Now comes time to build it.