Since Instagram's primary purpose is to post photos, there is no straightforward way to post a website URL in any photos or comments you post. However, it is still possible to add links on Instagram either by inserting a link in your profile bio, or by tagging people in photos or in captions.
Steps
Method 1 of 3: Insert a link in a bio

Step 1. Open the Instagram app

Step 2. Tap the icon

It represents the silhouette of a person and can be found in the lower right corner of the app.

Step 3. Select Edit Profile

Step 4. Choose Website

Step 5. Type the address of a site

Step 6. Select Save
This option is located in the upper right corner. You will return to the profile page. You should see the site address you entered under your username.
Method 2 of 3: Tag people in comments

Step 1. Tap the Instagram icon

Step 2. Select the icon

It represents the silhouette of a person and is located in the lower right corner of the app.

Step 3. Choose a photo
The photos are located under your username.

Step 4. Tap the Comments icon
It is located below the photo, to the right of the heart icon. You should see a blinking cursor in the titled field add a comment.

Step 5. Type a username
Instagram usernames begin with the @ symbol, for example @m monsieurx.

Step 6. Select Publish
This button is to the right of your comment. You should see the username in the comments field. Now users can click on that username to go to the profile of the person you've identified.
Method 3 of 3: Tag people in photos

Step 1. Select the Instagram icon

Step 2. Tap the icon

It represents the silhouette of a person and can be found in the lower right corner of the app.

Step 3. Choose a photo
The photos are located under your username.

Step 4. Press the three dots
They are located at the top right of the photo. A white window will appear.

Step 5. Select Edit
This button is located in the white popup window. A translucent cover that indicates Identify people will appear in the photo.

Step 6. Choose Identify People
The order appears in white on the photo. You will be prompted to tap the photo.
The tag will be placed where you tap

Step 7. Tap the photo
You will see an empty field with a blinking cursor.

Step 8. Enter a username
As you type, autofill will display a drop-down menu where you can choose the person to tag.

Step 9. Choose a username
Select the person from the drop-down menu. You will be redirected to the photo.

Step 10. Select Save
This option is located at the top right of the page. When you have pressed Save, the username you chose will appear in the photo. Visitors can click on the username to go to the page of the person you identified in the photo.