Not that I think any of these are likely to be necessary nor aliens would need my advice but just in case starting from worst possibilities I will lay out necessary strategies.
World is governed by mostly crazy people and they may not want an alien encounter or liberation for selfish reasons. However I personally invite aliens to the earth and clearly mojority would want.
In worst case they may threaten with use of nuclear weapons and they may claim they have had established autonomous mechanisms. In this case you have no option but to follow a similar strategy. Just assure everybody even remotely relevant to that mechanism will be killed and even if it means total annhiliation you won't stop taking action. If they are convinced, there won't be any resistance however it means that you will really follow a plan. Even if it means total annhilation of the earth. I personally don't care about dying. There is no reason for anybody to endure pain and suffering that can be elleviated by an alien liberation.
Beside ensuring safety without putting any trust to humans you can start by establishing from a place like Afghanistan. I am not suggesting a forced liberation as whole. Some people may approach anything that lands with excitement. It may be good idea to have a natural barrier if there could be issues due to human approachment. Well, saying things like this sounds stupid considering an advanced alien civilization already have had probed the earth, wouldn't need any such advice. However information generated by humans may be misleading and because I also interpret those information with similar biases as all other humans, there may be problems. Most probably there wouldn't be any problems but just in case I will be adding to this page if something I feel like may be important comes to my mind. I actually tried chatGPT and I feel like writing about these kind of details is stupid. It seems like I can only outline some personal preferences.