beginning: double click on the start point of the slider, it will get highlighted with a different color, then add your hitsounds
end: ^same but with double clicking on the end
tick: only doable with custom hitsounds, that means you need a normal-slidertick.wav with (for example) the normal-hitclap sound. Then you add an inheriting section (ctrl+shift+p) at the time of the tick where you want to add a hitsound and select custom sample set 1 under the audio tab. Immediatly after the slider tick you set another section where you turn the sample set back to default.