El to Addison! Red Line.

I think your closest station is Chicago and State.

If you intend to use public transport a bit, worth getting one of the 1, 3 or 7 days passes.

Single trips on the El cost $2.25.

Your closest station to Millennium Park is probably Monroe & State. Chicago & State would be a bit further north (about 1/2 mile).

You could also catch the Number 146 bus northbound at Michigan and Randolph. It will cost the same as the L, it's a little faster and is much more scenic as it runs express along Lake Shore Drive after it leaves the Mag Mile. Exit the bus at Addison and walk west about six blocks to Wrigley.

The bus stops are displayed above the windshield and at the flexible section of the bus and announced.

Hail cab to Wrigley Field. Cost $20.