You can easily install the apps once followed the below steps,

Requirements

1.    IPA file (app.IPA)
2.    Plist file (app.plist)
3.    Web server
4.    Large icon(512x512) & icon(57x57) png images

Getting Started

Step1:

Using attached profile, build & create IPA and PLIST file.
     
Product -> archive

When you create IPA last step, it'll ask this build is for enterprise app, here need to tick  Save for Enterprise Distribution , then popup will come like  attached screen.


We need to enter IPA URL, title, large & small image URL & PLIST will be generated automatically.

These IPA file & PLIST files have to upload in web server.

For example :

Application URL  : https://examplesite.com/app.IPA

Title : App Title

Large Image URL : https:// examplesite.com /512x512.png

Small Image URL: https:// examplesite.com /57x57.png

Step 2 :

Upload image files(57x57.png & 512x512.png), app.IPA and app.plist on web server

Step 3 :

For IIS,  use IIS Manager to add the MIME type in the Properties page of the server:

IPA application/octet-stream
plist text/xml

Step 4:

In web page, need to add link for downloading app   

<a href="itms-services://?action=download-manifest&url=http://example.com/ app.plist">Install App</a>

The above link need to give url of uploaded manifest file.

Now can click  on "Install App" link & install the app on  iOS devices.