Here I will brief you about feature activation using Power Shell script.
Consider a case where you want to activate a Site Collection Level feature on all site Collection of http://xyz.sharepoint.com
which have 300 site collection. Now Of course we would like to automate this process using console application or using powershell.
Please fine below is the one liner powershell script which will solve your purpose.
- Get-SPWebApplication [Web Application URL] | Get-SPSite -Limit ALL | ForEach-Object {Enable-SPFeature "[Feature Id]" -Url $_.Url -confirm:$False}
Replace the value for Web Application URL like http://XYZ.sharepoint.com and [Feature ID].