I'll help you enter the airfare for your volunteer activity with Global Volunteers: 

1.  Go to Federal, then Deductions and Credits.

2.  Select Charitable Donations, you'll see Donations to Charity in 2017, select.

3.  Answer YES, you want to make donations.

4.  Add the name of your charity, Global Volunteers.

5.  Go to ADD, Mileage and travel expenses.

6.  Fill in the description (trip to Poland to assist with...), date (once), and amount of fare, description of travel costs (airfare).

Please be aware that there are contribution limits generally of 50% of your adjusted gross income. 

The following IRS link may be helpful.  Especially refer to page 13 of this publication.

https://www.irs.gov/pub/irs-pdf/p526.pdf