Once DB Replacer is installed, you will be able to access it via the Regular Labs - DB Replacer menu link under Components.

Using DB Replacer is quite straightforward. You will be presented with the following component interface:

In the Tables select box, you will see the list of all the database tables of your Joomla installation.

Simply choose the table in which you want to make the changes. You can only search and replace in one table at a time.

By default, the Joomla content table is selected. The default selection can be changed in the DB Replacer Configuration Settings.

After selecting the table, the Columns select box will be populated.

You can choose one or more columns here. To select multiple columns, keep the CTRL (or Command for Mac) key pressed when selecting them.