Siskin IM is an XMPP client on IOS developed by Tigase Inc., which main business is their own XMPP server software. But the clients are free to anyone and can be used with any standards compliant XMPP server.

Here you can see how the registration/login looks like in SiskinIM:

This is the startup screen when you just installed Siskin IM.
If you already have an XMPP you can start with “Sign in to an existing XMPP account”.
Please follow the instructions in the documentation to register your account on hookipa.net.
Enter your XMPP domain here, for example “hookipa.net” and follow the next steps and enter your account and password.
After successfully logged in, Siskin will ask you some questions like displayed here:
Please enable Push Notifications and Message Archiving.
When done, you will see this screen:
Chats: here you can find your chats, be it 1:1 personal or Multi User Chats (chat rooms).
Contacts: here you have your contacts and can add new contacts
Settings: pretty obvious… you can change some settings here and below you can see some of those settings…
This screen can be found under Experimental settings. Basically you can enable all of them.
Depending on your Siskin IM version, there might be more or different settings.
This is the Chats setting page.
You should enable “File sharing via HTTP” if you want to send files/photos.
When “Encryption” set to OMEMO, all your chat messages will use End-to-End Encrtyption (E2EE). Your contact need to support this as well. Be aware that this may cause issues dependingon which software your contact is using.
Here you may want to enable “Auto-authorize contacts” to make your life easier. Otherwise you will need to authorize authentication requests when someone adds you as a contact.