How to connect multiple database ..??

I have two databases now. One is nopCommerce's database, another is mine. Because I have some special tables and it is used by another website.

How can I access two databases in the same time?

Thanks.

Version: 4.30

Is this you too?
https://www.nopcommerce.com/en/boards/topic/89331/i-have-two-databases-now-one-is-nopcommerces-database-another-is-mine-because-i-have-some-special-ta

(if so, please don't duplicate topics :)