I am looking at the tab for heart of gold on Songsterr and I've come across this bit
what does the legato notation means? Should I put two notes there or just one?
Very straight-forward: the first eighth is tied to the second eighth to create one quarter note. So you just play the first beat and "let it ring".
What you see here is not a legato bow, but a tie. The tab is written as one voice, so in order to write two eighth hi-hat hits, you need to write the bassdrum in 2 eighth notes too. To get around this issue, the second eighth note is then tied to the first to make it practically a quarter note.
The way you should play a bass drum is you kick down on the pedal and instantly release it. When you play a legato note on the bass drum, you keep the pedal on the skin (in your case for a quarter or an eighth note). You would play notes.
You would make sure you don't get legato direction confused with a tie. But, listening to the song many times, I have figured that it is, indeed, a legato instruction.