How can we test basic computer skills in an interview?

By giving some test. It can be useful and it don't take much time on interview

it depends on the work nature:

if it requires microsoft office skills , you give him/her a hard copy of an excel sheet to apply on computer

by give them paragraph or table and tell him or her to type it in different ways (excel, word, power point...etc)

A written test with different levels of difficulty would be engough.

well, we need to know his,her skills so we have to give the candidate an a4 letter content ( paragraph , table , numbers , etc ) 

* This is done by allowing the person to be interviewed using a single computer staff and give him some business and paragraphs that relate to the basic skills performed by the light of this and the extent of application of this work is evaluated if he has experience in computer skills or not.

Give candidate a short test from package of Microsoft Office, e.g.

1. WORD Test - Ask candidate to copy type a paragraph of about6 lines.  Check the accuracy of spelling, punctuation and grammar.

2. EXCEL Test - Ask candidate to copy data into a table, give it a heading and list items in some kind of order e.g. alphabetical or chronological.

3. OTHER PACKAGES - Ask candidate to perform a computer task which they would need to do in the job. 

4. EMAIL - Find out what the candidate understands about email etiquette and confidentiality.

5. PERSONA - Observe how candidate carries out tasks.  Is the candidate comfortable and confident doing the tasks, or is there hesitation and a long time taken to complete the tasks? Did the candidate take instructions well or did the candidate make excuses for not completing tasks?

6. WILLINGNESS TO LEARN - If a candidate demonstrates willingness to improve and learn new skills and is a quick learner, this is a good quality too.