How does the poem reveal a father's concern for his daughter?

Yeats's "A Prayer for My Daughter" does indeed show the concern of a father for his daughter, but in rather conventional terms. We must bear in mind that when the poem was written, in 1919, fathers were still generally expected to guide the life choices of their daughters, and Yeats is no different. This helps to explain why Yeats is so keen to see his daughter married off to a man of wealth and importance, a man of Ireland's Protestant Ascendancy whose world was such an endless source of fascination to the poet:

And may her bridegroom bring her to a house Where all’s accustomed, ceremonious;

Yeats's anxiety about his daughter's future marriage prospects is heightened further by the parlous state of the Protestant Ascendancy at this particular moment in Irish history. Ireland was in a state of revolutionary turmoil during 1919 and Yeats, though sympathetic to the cause of Irish nationalism, was at the same time concerned about the future political role of the old aristocratic families post-independence. He valued the stability which he thought the great families brought to the country. In an atmosphere of such violent revolutionary flux, he wants his daughter to be part of that solid foundation which he's come to believe is Ireland's only true hope. In that sense, Yeats's love for his daughter is inextricably linked with his somewhat idealized love of country.
https://poets.org/poem/prayer-my-daughter