You only need to open the port if you are connecting to that port remotely(from another PC which is not on the same network). There's no need to open any port if you are testing on the same machine.
https://forum.ragezone.com/f82/mu-ma...0/#post8446660
In the link above is the information for allocating and enabling the SQL to use a defined port and enabling the TCP/IP to be able to connect to SQL from a network (1433 which is the default port used).
On a VPS, you need to set the inbounds and outbounds rules for port 1433 and enable and set the port for SQL (similar set up as the post from that link is saying).
The port-forwarding is usually called "Opening ports" on your personal computer or VM running on a computer because you are connecting to Internet through a router, so port forwarding must be done from your router's management software(accessed by browser in most cases).
Your error "Login failed for user 'admin'" is actually what is says. This SQL user is not existing or you didn't set this user's permissions to access that database as SQL administrator into SQL Server.
Also, make sure your editor's config file is set up correctly. Some of the editors are using ODBC, others are using SQL connection with databases' names.