शोकपरितापेन by lamenting, मृतः the dead, श्रेयसा with wellbeing, न युज्यते will not gain, अत्र here, यत् whatever, अनन्तरम् later, कार्यम् should be done, तत् that, समाधातुम् to take up, अर्हथ you may do.

'No lamentation revives the dead. So you should take up whatever is required now.