If it's just a current distribution of cash:

1. Enter the amount for Cash and marketable securities as usual under Balance Sheet, M-1, M-2 > Sch M-2 (Capital Account);
2. Click on the Special Allocations tab and override the allocation for Cash & Marketable Securities (enter total in Sch M-2 (Capital Account)) either by Amount or Percentage;
3. Click on Input Return, go to Partner Information > Partner Percentages, and update the ENDING percentages as necessary.