The same as if they were working in the US.

Then consider whether foreign earned income exclusion or foreign tax credit may apply.

Most likely you won't be dealing with a W2 unless it's a US company.  With ProSeries enter the income in the wages, salaries tips worksheet...you'll have to dig a little to find that, not like in the past when ProSeries allowed us to customize the forms to our liking, not to theirs and I would have that as a commonly-used form...

...oh, where was I?

Also be aware if client paid in US dollars or some other currency and convert appropriately. Determine best method, exclusion or credit or possibly, credit on excess nonexcluded amount also.