Lightspeed does not provide a solution to import weight or dimensions into the Web Store Tab. Hyperspace offers tools that can append existing products in Lightspeed with this information.
The first step is to get an export of all product data that exists in Lightspeed. The weight/dimension import requires that you have the SYSTEM ID as the first column for the import.
Simple products and children products in Lightspeed all have a SYSTEM ID.
Often the easiest way to get a list of all products you want to update is through Lightspeed's own export. If you login to Lightspeed and go to Inventory > Item Search you will see a list of all products and you can even narrow down the list.
Click the Export tab on the far right to export your selection to a .csv. Open this file in excel to edit.
Download this file and copy and paste the SYSTEM ID and Product title from your Lightspeed export into this sheet. Fill out the other columns as needed.
A. Do not change the names in the column headers.
B. Do not re-order the columns.
C. Do not add new columns.
When you are done, save the sheet as a .csv.
Login to your Hyperspace account and click on the Data Import tab at the top.
At the bottom, click the button called: Update Dimensions/Weight
Choose the file on your computer and select Import.
Depending on the total number of rows in your file, it could take minutes or several hours for the update file to finish importing all of your data.