Go to the "Variables" section
Make sure the Container ID is listed under the Build-In Variables
Create "User defined variables" following this scheme:
Type of variable: Data layer variable
Name of the data layer variable: indicate the value you set up in your custom dimension on GA4 in the event parameter field (ex: adloop_click_1).
And give it an adloop related name
Repeat these operations for all custom dimensions created in GA
Open the configuration of the "Google Analytics settings" variable,
In "More Settings -> Custom Dimensions, click on "Add Custom Dimension"
Fill in the following information:
Index: XX (where "XX" is the index of the dimension created on GA)
Dimension value: {{adloop_click_XX}} (Use the brick to choose the previously created variable)
Repeat these operations for all variables created in GTM
Go to the "Tags" section and add a new tag of type "Custom HTML", with the name "Adloop tag".
Copy and paste the content provided on the Adloop interface into the "HTML" field of the tag
Save the tag without trigger
Open the configuration of the Google Analytics tag with the largest trigger ("All pages" or “Pageviews” for example).
In the advanced settings of this tag, in "Tag sequencing", check "Trigger a tag before Google Analytics is triggered" and choose the "Adloop tag" previously created
For your GA4 events (purchase, add to cart, view item etc.) set-up on GTM, add the Adloop event parameters & values :
adloop_click_1 and for the value select the first user defined variable you created previously using the brick button
adloop_click_1_meta and for the value select the second user defined variable you created previously using the brick button
Note: the name of the value between {{ }} depends on how you named your user defined variable ; it might be different from the screenshot above.