I cannot annex Indian state, only "force migration"

Question:

I made my first colony in Brasil and I occupied land of some "Tapuia" Indians neighboring to my colony. But in peace negotiations I see only "Force migration". I cannot annex them or claim the province. What is the problem? Perhaps I have wrong casus belli. It seems I'm unable to get "conquest" casus belli against Indians?

• Do I need research some tech/idea for that?
• Maybe I need create some "core" in Americas first? How can I do that? Do I need to grow the colony to "City" first?

background (not necessary to read):

I play play Bohemia at year 1530 - it took me long time to get to the sea. I started to think about colonization only after I became HRE Emperor and annexed Burgundy (including Holland). I terribly lag behind Portugal, Castil, England and even France in colonization. But my army is strongest in Europe (4000 man stronger than France and Ottomans).

In general I find it very hard to grow colonies (it is extremely slow, all other nations grow colonies much faster). I was thinking that by conquest of Indian lands can compensate my lack of exploration/expansion ideas, using strength of my army.

I have researched only "exploration" idea to "Quest for New world" stage. I don't have "expansion idea" yet. I have barely colonial reach to touch America (just Antilles + apex of Brasil).

Before I finished "Offensive" ideas, and picked "Influence" (which I regret, since I would prefer colonization over influence, but that was before I claimed Holland).