First press New Career on the main menu, confirm all the manager details and in the settings set the transfers strictness to loose then move onto the screen where you select a team.
Personally I selected Manchester Utd as they have a high reputation and have a large transfer budget.
Once your game loads in go across to transfers tab and select search players. In the player name tab type in 'Aidonis' the player Antonis Aidonis should come up. Select him then select him again in the transfer network page and press 'Shortlist & view in Transfer Hub'.
Select him in the shortlist tab and press 'Approach to loan', once the negotiating starts press 'Loan-to-buy', press '1-year', then they will ask how they wage split will work. Change it so you will pay 100% and the parent club will pay 0%. Then whatever suggestion they ask for in the future transfer fee press accept, if they dont suggest any price you should press propose transfer fee and put £500,000 and then they should accept.
Next you will need to advance a few days until he joins the club on loan, once he joins go across to the squad tab and press 'squad hub' scroll down to Aidonis (he is a CB) select him and press on 'Settle Buy Option' and press the agreed on transfer value.
Next you'll need to press negotiate to discuss his wage with his agent, either agree with everything they ask for otherwise follow these instructions. Select 'prospect' for team role, give him a 4 year contract, disregard release clause and give him a wage of £7,500 with a signing fee of £100,000.
Hopefully that should do the trick and then your achievement should then pop, fingers crossed this has been helpful and please comment if anything needs updating. It's my first guide so be kind 😁😂