NET Framework 3.5 is a 'silent' feature in Windows 10 it as been left in for legacy apps, to enable it go to Control Panel, select 'Programs and Features' on the left hand panel you should see 'Turn Windows features on or off' click on that wording, a box will pop up at the very top are the .NET Framework features put a tick in the selection box for NET 3.5 and select OK windows will enable the feature for you, a computer restart may be required.
as far as importing your asset into GG you will not see anything until you select a texture for it
Welcome to the real world!
Main PC - Windows 10 Pro x64 - Core i7-9700K @4.2GHz - 64GB DDR4 RAM - GeForce RTX 2070 SUPER 8GB - 2TB NVe, 1TB NVe, 2TB Hybrid Data Drive
Test PC - Windows 10 Pro x64 - Core i7-7700K @4.2GHz - 32GB DDR4 RAM - GeForce GTX 1060-6G 6GB - 1TB NVe SSD
Laptop - Helios 300 Predator - i7 7700HQ - 32GB - Nvidia GTX1060 6GB - 525GB M2 - 500 SSD - 17.3" IPS LED Panel - Windows 10 Pro x64
Various Tutorials by me