Unable to install any plugins

I'm a first time octopi user and I'm trying install plugins, but unable to do so. I can't install any plugin.

I'm completely new to this, so kindly help me out.

I'm afraid we can't help you without more information, such as what version of OctoPrint you have, what you have it installed on, maybe some logs would be really really helpful - they will likely tell the story.
Please describe exactly what is happening, what loads and what doesn't, there's a lot of factors that 'it doesn't work' doesn't really help.

Please also check your power supply for the Pi is up to scratch, it should be 5.1V and 2.4A (Pi3 or below) or 3A (Pi4).