Many e-commerce platforms such as Lightspeed, CCV Shop, Shopify and Magento shoot transaction data to Google Analytics by default. If you don't see any transaction data appearing in Analytics there could be 2 things going on:

You can easily check this by looking to see if you do see visitor numbers in Analytics. Do you see this data coming in? Then the tracking code is correct and you will need to turn on E-commerce tracking in Analytics. You can read how to do this in the next step.

However, do you see no visitor data? Then your tracking code is not properly set. In that case, contact your webshop platform and ask where you can enter the Analytics code. This can often be done under the heading settings at the back of your shop.

It is possible that your Analytics is set up correctly on your webshop but that you have not yet let Google Analytics know that you are a webshop. By default, transactions are not measured, but you can easily turn this on by using a button in Analytics.

Go to https://analytics.google.com/analytics/web/ and log in with the account that gives you access to Google Analytics. Then go to E-commerce and overview. If you have not set this up yet you will see a message appear:

You can set up e-commerce tracking by clicking on "Admin" at the bottom left.

Then click on "E-commerce Settings" under the profile of your website.

Once you have clicked on this, you will be directed to a page where you can turn on e-commerce. Click on the slider "Enable Ecommerce" and you will see a new slider appear: "Enable Enhanced Ecommerce Reporting".

If your shop uses Enhanced Ecommerce you can also turn this slider on.

With Enhanced Ecommerce you have more advanced reports available in Analytics, but many shopping platforms do not support this out of the box. Not sure if your shop uses this? Then leave this option off.