This is how I do it with Angular 5 and ng-bootstrap. Create your modal component as follows:

import { Component, OnInit } from '@angular/core';
import {NgbActiveModal} from '@ng-bootstrap/ng-bootstrap';

@Component({
  selector: 'sm-create-asset-modal',
  templateUrl: './create-asset-modal.component.html',
  styleUrls: ['./create-asset-modal.component.css']
})
export class CreateAssetModalComponent implements OnInit {

  constructor(public activeModal: NgbActiveModal) { }

  ngOnInit() {
  }
}

and the template will be something like:

<div class="modal-header">
  <h4 class="modal-title">Create New </h4>
  <button type="button" class="close" aria-label="Close" (click)="activeModal.dismiss('Cross click')">
    <span aria-hidden="true">&times;</span>
  </button>
</div>
<div class="modal-body">
  <p>One fine body&hellip;</p>
</div>
<div class="modal-footer">
  <button type="button" class="btn btn-success" (click)="activeModal.close('Close click')">Create</button>
</div>

In the component where you want to open the modal from add a variable of type NgbModal and call open as follows:

export class MyComponent {
  constructor(private modal: NgbModal) {}

  onClick() {
    this.modal.open(CreateAssetModalComponent);
  }

}

In the NgModule where the CreateAssetModalComponent is declared add the component in the entryComponents array as follows:

@NgModule({
  imports: [...],
  declarations: [CreateAssetModalComponent],
  entryComponents: [CreateAssetModalComponent]
})

Assuming you have other Modules like NgbModule imported this should work.

I'm not sure I fully understand what you are trying to do but in the essence it is very simple - to open a modal window with a specific content you just call the open method on the NgbModal service. The simplest possible implementation would be a one-liner (this.modalService.open('Hi tehre!');):

@Component({
  selector: 'my-home',
  templateUrl: 'src/modal-basic.html'
})
export class HomeComponent implements OnInit {
  constructor(private modalService: NgbModal) {}

  ngOnInit(content) {
    this.modalService.open('Hi tehre!');
  }
}

See it live in plunker: http://plnkr.co/edit/5qq04Q4HFLOe9tsyeMMI?p=preview

It is exactly the same as in angular-ui/bootstrap for AngularJS 1.x! Principles are exactly the same, nothing have changed.

What might be giving you headaches is how to specify content of the modal. In the above example I'm using a string but in vast majority of cases you want to use HTML with bindings, directives etc. But Angular is different as you just can't pass HTML string if you don't want to ship compiler to production (and you really don't want to do this...).

So your next best option is to use another component as content, here is a minimal example: http://plnkr.co/edit/EJyZ6nF5WVAS9bvQycQe?p=preview

Note: due to a bug in the Angular itself you need to currently wrap the open() method call with the setTimeout. Bug reference: https://github.com/angular/angular/issues/15634

Add the HelloHomeModalComponent to your constructor parameters and call the open function from HomeComponent like so:

import { Component, OnInit } from '@angular/core';
import { HelloHomeModalComponent } from "hello-home-modal.component";

@Component({
    selector: 'my-home',
    templateUrl: './home.component.html'
})

export class HomeComponent implements OnInit {
    constructor(private modal: HelloHomeModalComponent) {}

    ngOnInit() {
        this.modal.open();
    }
}

You don't need to pass a content parameter to your component's open() if you use @ViewRef() to get the appropriate template reference from the modal component.