In SSMS, open a new query window ( Ctrl + n ), make sure the database is selected from the drop-down list of databases ( Ctrl + d to focus on the list, then up / down arrows and Enter to select the database), write down the query and F5 for start.
You can use the mouse for all of the above (there is a button on the toolbar for the new query window, and you can use the mouse to select the database).
An alternative is to use the object browser to drill down on the database and table, right-click on the table name and select the option "Select top 1000 rows ..." (or similar).
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