This can 1) be a plain statement that the Spirit was in the form of a dove (see UDB) or 2) be a simile that compares the Spirit coming down upon Jesus gently, the way a dove would. (See: [[rc://en/ta/man/translate/figs-simile]])
This marks the beginning of another event in the larger story. It may involve different people than the previous events. Your language may have a way of doing this.