Can I boost my computers 4 GB ram 8GB (I have one empty ram slot) Company: Lenovo Type: note book?

Yes

I usually go to Crucial's website and use their RAM tool to see what exactly my computer can support.

Or other memory companies have such tools too.

Or you can check the manufacturer's website as well.

With exact model number [it is on the back nameplate] Lenovo's webiste can answer this