I have my old seed, how i can use it?

[Krypto]

i have installed sia ui version 1.3.0
I have only the seed, no password.
Last month i opend the old sia wallet with my seed and the balance appears, it was ok.
But i never understand this wallet, why i have to put this vero long seed to get into the wallet.
Now the wallet ask foe a pasword, but i never had one.

thx for help :-)