How to generate iOS ssl certificate?

I have setup seafile server and can access through https
Then I install seafile pro on my iphone but when I try to login, it pops up message “Seafile can’t verify the identify of the website www.xxx.com
Can anybody guide me how to generate iOS client certificate?
Somehow when I import certificate seahub.crt, always get wrong password

@dony71 You need a valid sever certificate, it has nothing to do with your iOS device. You can get a free valid certificate from e.g. Letsencrypt or you can turn off the certificate checking in your client:

Sorry it is in german here, but I think you will find it anyway.