Here is a good resource to explain the form that David was talking about:
Although the teachers call it narrative present tense, it is more commonly referred to (or at least in my experience) as plain form, or diary form. It is also commonly used in TV documentaries. Even though the teachers say it should only be used in informal situations, which is true when spoken, it is a kind of neutral form when used in writing (because you don't know who will be reading your paper), which you should use for the TOPIK.
To sum up the main points of it:
~저 should be turned into 나. It's not considered rude in this case, just neutral.
~For action verbs without a final consonant, add ㄴ다 at the end. For example, 저는 한국어를 배웁니다. --> 나는 한국어를 배운다. (배우다 being the original verb)
~For action verbs with a final consonant other than ㄹ, add 는다 at the end. For example, 창문을 닫습니다. --> 창문을 닫는다. (original verb being 닫다)
~For action verbs ending with ㄹ, drop it and add 는다. For example, 꽃을 팝니다. --> 꽃을 파는다. (original verb is 팔다) ((I'm having a sudden moment of low confidence in my beginner Korean knowledge, not sure if the 존댓말 form is 팝니다 or 팔습니다 :P))
~For descriptive verbs, or 있다/없다, just keep them in their dictionary form. For example, 저는 요즘 바쁩니다 --> 나는 요즘 바쁘다. (verb is 바쁘다)
Hope this helps!