Quoting Peter Gurk:
Last year, in utter ignorance, we laid down a totally different seed in our
lawn that has resulted in a patchwork lawn. I'm trying to determine if this
is something I can remedy myself easily..?

I've done some searching on the net to no avail. Thanks in advance for any
advice you can provide!

There are a number of things one can do to favor a particular grass in
the lawn over another, including watering habits, fertilization
timing/frequency, and mowing height. However, it's going to be
impossible to specifically answer your question without knowing what
types of grass you're personally dealing with.

So, what was your base lawn before putting down the seed? St Aug,
Bermuda? (guessing based on your headers - you seem to be in the south).

And, what kind of seed did you put down?