Replacing bleed valve

[New2DIY123]

I've replaced the radiator bleed valve. I didn't have any PTFE tape so I just screwed it in. I noticed when I went to bleed it. The entire valve turns. I tried to tighten it but it's turns when I try to bleed it. What can I do now? Isolate and use the PTFE? Or do I need something else?

 

[terryplumb]

Tighten it with a spanner. Then hold it with spanner whilst opening valve with a key. The valve has probably been overtightened with the key.
By the way there should be a rubber seal between the rad and valve body ,is there one ?

 

[New2DIY123]

Thank you terryplumb. Your answer helped. The valve points towards the wall and I initially used a spanner which was for bigger valves. I used a smaller spanner and now I could actually tighten the valve fully. I tested bleeding it few times and it was fine.