Not able to Install Package ?

One of the easiest way to install package -

Steps:
Go to the below URL:
https://login.salesforce.com/packaging/installPackage.apexp?p0=04txxxxxxxxxxxxxx
Replace 04txxxxxxxxxxxxxx your package id | Next | Install
and that's it.
https://login.salesforce.com/ - Salesforce login URL
04txxxxxxxxxxxxxx - package id

Another Approach in Visual : https://youtu.be/laQe6a2oiuU (You have to just provide the ID of the Package)