In this article, we see about Trust relationship between two domains in Server 2016.
So, first we link both two domains in active directory and trust and Domain A and Domain B have administrators Rights. They can easily create One-way and Two Way Trust relationship.Before proceeding, you need to ensure that the networks/forest on both sides have access to each others DNS information! Otherwise, you will never succeed. DNS will contain all of the SVR records that the trusts will rely on. Typically, this is done by creating a domain forwarder between each DNS zone (e.g., DNS A will have a forwarder setup to DNS B in forest B and DNS B will have a forwarder to DNS A in forest A).
First open Server Manager and click Active Directory domains and trusts. this is Domain A.
Right click Domain A and click properties

Click Trust and Click New Trust

Click Next to New trust Wizard.
Now enter the Domain name of B and click Next. Here We enter the DNS name has Techpro.com
Select Trust Type and click Next.
Select Transitivity Trust and click Next
Select Direction of trust, here we select Two-way and click Next.
Now enter the password for trust between two domains and Next.
Now trust Selections Completed and click Next.
Click Finish for completing the new trust wizard.