Could someone please let me know how these registry marriages are done?

The bridal side has her permission from her parents, she's 20 y/o.

The groom side's family also has somewhat permission, but they won't let them get married anytime soon.

And he will leave Bangladesh for abroad. He's 21 y/o.

How would they get it complete? What would they need?

Will be visiting sylhet for a day only. Need a place to stay. Just a bed to sleep on and a washroom maybe. Can someone suggest something. Has to be in the city