To add a Work Record to a site through the data grid, you must first select the sites site via the checkmarks at the left side of each record you wish to add a work record to.
Then after the site is selected, click the Add Work button in the panel to the left of the data grid.
From here, you will be brought to the work record page where you can either fill out the information manually, or if you need to use a previous work record that you have viewed, you can use the Load Last Work Record button at the top of the window to load the information from the last work record you viewed.