How can I enter a sell transaction?

What I tried:

• tap menu button, bottom-right
• "Select Portfolio"
• tap "pencil and paper" button to go to edit mode
• tap portfolio where I want to enter transaction
• tap stock position where I want to enter transaction
• tap + button

Now all I can enter here are shares, price, commission. There is no selector for buy/sell and it always defaults to Buy@, even if I enter a negative share amount.

Any ideas?

PS: I saw a while back there was a Youtube link posted showing how to enter transactions. I'm in China currently and YT is blocked here. Please give a verbal description. Thanks!