Football Manager 2020

On the left-hand menu click on "Scouting", then on the top bar, click on "Assignments".

Check if you have the Scouting Responsibility set to yourself and it's not delegated to one of your staff members. You do that by clicking on "Scouting Responsibility" and your manager's name should be listed under "Assigning Scouts". If it isn't, click "Take Control".

Now click on "+ Create new assignment". On the left, you have three options to scout, select "Match". If there is a suitable match in the next three days, it will appear on the right side (if there is no suitable matches, try again in a few days). Click on the "No action" dropdown menu and select "Scout match" and one of your scout's names. Confirm by clicking "Start Assignment".

Continue the game and wait until the game date passes and the match should be scouted. The achievement pops automatically.

in your news feed you will occasionally get notified of certain events like trial days that include players recommended for you by your scouts, you will have the option of attending the game or sending your scout.

send your scout, keep progressing your game further and once the game is finished, achievement is yours!