Well, first thing - which you probably already know - is to have the guitar tuned to an open chord. You could start off with GBDGBD from lowest string to highest.
The other thing is to have a feel for placing the
slide/steel on the strings - it's just enough pressure to allow the string to vibrate between the point where the metal touches the string and the bridge, but not so much where you're actually pressing down against the frets. Think of the slide/steel as a 'hovering, moveable fret.'
And when you position the slide or steel, it would be right over the fret as much as possible, instead of behind the fret like when you're fretting the guitar the regular way.
For the chords you play, just keep it simple, using the I-IV-V progression. Like you'd play stuff, pick or fingerpick notes, with all strings open, and then place the slide and slide up quickly to the 5th fret (to get the IV chord), and then up to the 7th fret (for the V chord), and basically get used to the feel and sound of it.
I don't know about your particular guitar, but on most regular guitars, the strings, if you were to look edge-on from the headstock, are arranged in a slight curve to match the curve of the frets/fretboard. And if you look at the slide/steel, it's dead straight (unless you have one of those concave Dunlop slides), and so laying the slide across the strings, you'll realize that the flat doesn't quite cover all the curve of the strings. Some will rattle. Like if you've got the slide to cover the top three strings, the bottom three will be only slightly touched or not touched at all - like a boat angling back and forth as it goes through waves.
The same if you're playing the bottom three strings - the top ones will rattle a bit. It's just something to be aware of.
If you've got a guitar that's setup to be a slider, like a lap steel or pedal steel or reso for instance, you'll notice that the tops of the strings are dead-even so it'll match the slide/steel. That way there's no rattle.
But then again, rattle is part of certain styles of slide playing.
Anyhow, hope this helps. Just fool around with it and you'll get the feel for it.
Best regards...