How should I prepare for TAPMI WAT n PI?

TAPMI’s WAT includes questions that are mostly related to general knowledge and current affairs. WAT is basically how strong you are in written skills. Try reading current affairs topics from there only. It's all about how you tell them. Write clearly point to point and do not use jargon or bug words. They don't fetch any more points. Just make your point clear.

PI mostly has questions derived from your past experiences, academics, and sometimes current happenings around the world. If you’re aware of and following at least one news source for around 4 months before your PI, you are good to go.

Read the form that you filled out. That's the first thing they are going to ask. Be confident and do not try to beat around the bush. If you do not know something it's ok as long as you say it. But that being said, do not go completely blank.