How does this consensus thing work?
Consensus is a
general agreement. Rules that you have to follow such as 21,000,000 coins, halving every 210,000 blocks, block generation every 10 minutes on average etc. If you don't follow these rules, you're not part of the Bitcoin's block chain.
How would I become a part of this consensus?
I guess you mean Bitcoin's? By running a node that is compatible with Bitcoin's consensus rules. Here's a bitcoin client:
Bitcoin Core.
How is the incentive for mining going to be preserved after the coin creation is not enough?
Miners' incentive will then be the transaction fees. It'll always be profitable for some nodes to support the network. We may see huge increases of the median fee in the future. We may also not. Lightning Network solves the scaling problem to an extent and I hope that from now up to 10 years, there'll be a serious LN adoption. It'd be great if half of the mempool transactions were broadcasted to open or close a channel.
If you're a beginner to Bitcoin (or don't how LN works), here's a nice thread about the basics of LN:
Basics of the Lightning Network.
Can consensus create more coin for mining incentive? Without mining bitcoin will collapse, right?
No and no. I answered you above why.