First of all you have to get tested for COVID-19( RTPCR/TRUNAT) followed by if positive you can wait till your report comes negative,after 21 days of negative report you can donate plasma depending upon your antibody titre.
And the last thing now it's least recommended to donate plasma for COVID patients as it's efficacy is not helpful.
Next Steps
Antibody testing is not futile and there will not be any risk of catching COVID infection.
Health Tips
Stay safe and healthy.