We don't specify it here, but in almost all cases you should provide an --admin address when instantiating a contract. If you do not, you will not be able to migrate the contract later.
CosmWasm Smart Contracts take their arguments as serialized JSON. This can be created a number of ways, but as we showed in the previous examples, it may well be easiest to use the node command line, if that is available to you.
There is a Typescript helpers file for most contracts, and extensions for CosmJS, but at the time of writing, they are broken. This will no doubt be fixed soon, providing an alternative way of interacting with contracts other than the CLI.